Does bare drywall need to be primed before painting?

Question: Is it necessary to prime bare drywall before painting?  And do we need to prime existing textured, painted walls before we mud over them?
Answer: Yes, you need to use a drywall sealer on bare drywall.  Using a primer or a sealer would also help blend in the differences with the existing surface you want to cover.
http://www.ehow.com/about_6636020_drywall-sealer-vs_-primer.html
Comment: You should definitely prime the walls first. The mud joints soak up the paint and it would take several coats over any mudded area to look uniform with the rest of the walls. Do yourself a favor. Don't listen to these guys that are flipping houses. They are out to make a quick buck. Do it right by priming the walls. Better yet, try your own experiment. You'll see Conor Boyd and I are correct.
Comment: I respectfully disagree, you can pint on bare drywall no problem.  See my answer.
Comment: For what it's worth, the "paint plus primer" paints seem to vary in their ability to actually cover the drywall. In my experience the darker/stronger colors need tinted primer or else you end up with 4 coats of "paint plus primer" to get the coverage you need. In other words: use a good primer and save yourself some extra money on your paint.
Answer: In the UK, you don't need to prime bare drywall or plaster before painting with normal emulsion paint. However the first coat will soak in and you will need a few more coats.  (If you are using a very high spec paint that is thicker you may find that the first coat does not stick well without a mist coat, but I would always use a cheap paint for the first coat anyway.)
The normal advice is to use cheap MATT emulsion paint, watered down a bit, for the first coat as this will act as a sealer.  Also if the plaster has been polished and is very smooth give it a quick light sanding will help any paint to stick well.
Answer: You do not need to use a Primer on bare drywall.  I have painted numerous new houses, including mine, over the last 10 years and never have I primed the bare drywall.  No issues what so ever. 2 coats of any good latex paint will be fine, no question.
If you were going to be painting over existing paint, it would certainly help and can save an extra coat or two of the new color.  Also a good thing if you are painting over a wall that had wallpaper removed.  Also good if you are paining on really old walls that are extremely dry and may soak up a lot of paint.  But it doesn't sound like any of that applies to you.
People will argue that Primer is cheaper than good paint, so use the primer and save a coat of the expensive stuff.  I can see that argument.  But in my case, I would rather save time and stick to the same paint, rather than having to clean all the equipment and start over, especially if you are doing it the same day.
For your second question, primer might be a good idea before you mud over the textured / painted walls.  Mud sometimes has a hard time sticking to painted surfaces.  You could also give it a light sand that would help it stick.  We reciently had to have our ceiling redone, and the drywaller had concerns about it sticking.  Rather than priming it, he did a light sand, then used DuraBond to mud the ceiling rather than standard joint coumpound.  DuraBond supposedly makes a better bond, seals out moisture/humidity, and reduce cracks/blemishes over standard compound.
Good Luck!
Comment: Primer also has the advantage of drying faster so you can put your next coat on sooner.
Comment: hey cool, didn't know about the time to dry.
Comment: I will give you a +1 because you are right, you don't *NEED* to prime first. But I would argue it is a good idea to do it if you can.
Answer: My wife and I had our kitchen renovated just this past month and we told the contractor we would do all the painting of walls and trim as my wife is very meticulous, has a good steady hand, and an exceptional eye for detail.
We choose one of the best One Coat Cover paints on the market and figured we wouldn't have to prime/seal the drywall first. We were so wrong. Several coats of paint later we could still see different shades of the color over the seams and wherever else there was joint compound.
Then to make it worse, we splashed water from the sink sprayer onto the wall and when we wiped it off it revealed yet another shade of our color where the wall had gotten wet. So now we are in the process of repainting, first with primer/sealer and then with the original paint. Our mistake cost us over $100.00 and two week-ends. So yes, Prime/seal bare drywall!
Comment: If I could upvote more than once I would. ALWAYS PRIME DRYWALL!!!
Answer: Well you don't need to do anything -- in fact you don't need to put drywall up but you should prime drywall if you want a better finish on the wall. It seals the paper and seams. You often see a color variation or see the seams if you don't seal the wall. Sealing with a primer makes the whole wall the same surface that the paint can adhere to giving you a more uniform look. Have you ever gotten really close to a wall and looked down the side and you could tell where the seams were? They probably didn't use a primer.
Answer: you dont need to prime finished walls with paint on them if they are in good shape, but you should - it will save you finding out they arent.
as to priming fresh drywall, your answer is yes.  but whats really interesting is seeing some of the answers that say no.
i cant figure out their logic.  i have been in the general contracting business for 20 plus years, installed or had installed for me literally hundreds of thousands of square feet of drywall.  i have seen every possible type of drywall installation and the one universal rule is value.  you have to make a profit in a competitive market, which means giving good product at a competitive price.  the only way to do that is 2 or even 3 coats of a good sealer/primer (depends on if you are going for a level 3,4 or 5 finish) and then 2,3,4,5 coats of paint (reds and oranges need a lot more paint).  we almost universally spray paint on with a gun system and then overroll the very last coat with a very low knap roller.  however, for the purposes of this discussion, it will make no difference as to how its applied, as labour is labour - however you do it you want to minimize it.
primer serves 3 purposes - promotes adhesion, reduces absorption of surface coats, and reduces surface changes and imperfections, particularly at the transition between surface paper and the fillers used.
primer by design is less costly but not able to have a sheen (too many coarse particulates).  on the other hand, it has more polymerizing agents which make it seal the paper and fillers with less material.  if you don't use primer, you will be using much more paint per square foot for the finished surface, or you will be using a much more expensive paint (essentially primers bonders and sealers mixed with paint and its pigments).
from a business perspective, it may seem logical to use a more expensive one-coat type paint instead of the standard primer and paint approach, but the economics of it dont work out.  these paints are so much more costly than standard primer and paint, that it doesnt balance out in the labour savings.  with the caveat that if you are really, really slow at painting or so meticulous it hurts, then you could make the argument that that type of paint is worth the cost.  i would argue that its time to fire yourself and get some competent painters in.
from a finish perspective, its also vital that your surface be smooth and uniform.  primer is a critical part of this.  if you omit the primer step, you will have dramatic sheen changes on paper and on filler.  thats a huge problem and will usually result in you redoing it for free.
hope that helps
Answer: We've prep-coated drywall, and even putty coated drywall, and checked it out with a 500 watt light sideways on the dry wall to show all defects and still primed the walls. If you don't the paint can burn though your prep coat and you will still halve to paint again or spray more prep coat.
Always use a good primer.
Answer: This question depends on the situation. If the wall you are painting is the interior side of an exterior wall, it is a good idea to use a paint that provides a sealer for moisture. Brick and stone both have a tendency to sweat and under humid conditions your paint on interior walls that have not been "sealed" can bubble. Once moisture gets behind latex it can be troublesome and you may end up having to peel off the latex, repaint the drywall using Kills or a moisture barrier type paint, then repainting the area.
It is best to get into practicing quality work the first time around and I would recommend sealing your drywall and also caulking where needed. Do you have to do this? of course not, I guess it all depends on your piece of mind. For me knowing I went the extra mile to have a lasting paint job is part of the pride of doing good work. Trying to save time often can work against you.
Answer: So many yes's and no's...
My advice is... Just prime it, even with a cheap paint at a ratio of 80:20 (paint:water), I also like to put a glug of PVA in too and mix it all up, especially on moisture resistant plasterboard in bathrooms/ensuites (To help the key)
The reason I add a bit of PVA glue (carpenters glue) mostly is that even after a flash coat on new plaster or drywall filler/cement joints (Or "mud") is that I find it does help against any suction when applying further coats, and thus, a more even application, whilst still achieving a masking effect over the contrasting board/mud colours.
It is ultimately something I like to do, be it drywall or new wet plaster finished walls.
Comment: Yes, there have been so many yes's and no's, and it doesn't feel like your answer says much of anything that hasn't already been said, though adding "PVA" (is that a reference to standard carpenter's glue?) is unique. Maybe [edit] your post to expand on that point in particular - i.e. what is this buying you for the added inconvenience of painting with glue.


Who was the first to calculate $\pi$?

Question: I am very interested in the history of $\pi$. I am first trying to find out who calculated it. Many sources have different answers, from the ancient Egyptians, to Archimedes, to the Babylonians. I still can't find an answer to who first discovered $\pi$, or found a way to calculate it to any degree of accuracy. So who, or which group of people, were the first one(s) to discover/calculate $\pi$?
Comment: Nobody. Decimal expansion of $\pi$ has infinitely many digits and no pattern is known for them. Are you asking who first came up with a limit formula that can calculate it with any accuracy in principle?
Comment: It's pretty trivial to notice that pi is about 3 based on stuff like wrapping a rope around a tree. I doubt that that you are going to find a first person who estimated it.
Comment: To what degree of accuracy? If you want $\frac{22}{7}$, you'll have a very different answer than if you were to want $3.14159$.
Comment: To any degree of accuracy
Comment: @conifold: even better, **it is known that there is no pattern**
Comment: Perhaps we should admit that Ludolph computed the Ludolphian number... http://www.calculatoredge.com/math/mathhistory/historyans27.htm
Comment: @PeterMasiar The normalcy of $\pi$ is only a conjecture. There's a pattern of sorts in hexadecimal: https://en.wikipedia.org/wiki/Bailey–Borwein–Plouffe_formula But since $\pi$ is irrational, the digits don't loop.
Answer: It depends on the meaning of "calculate", since $\pi$ is a transcendental number it can not be "calculated" in the usual meaning of the word.
The first analytic formula (in the form of an infinite series) that in principle can calculate $\pi$ to any required accuracy is probably due to medieval Indian mathematician Madhava, who was first to conceive of infinite series explicitly, or one of his successors. In Europe this series was rediscovered by Leibniz, and is usually called Leibniz series in Western literature.
A semi-geometric "calculation" procedure capable in principle of producing arbitrary accuracy is much older. It consists of approximating a circle by inscribed and circumscribed polygons, and can be traced to ancient Greek orator Antiphon the Sophist. This method was mathematically justified by Eudoxus of Cnidus using what is now called method of exhaustion, and his justification is presented in Book XII of Euclid's Elements. Archimedes perfected the method in On the Measurement of the Circle. He proved rigorously that the ratio of the circle to the square on its radius was the same as the ratio of the circumference to the diameter, so it could be computed both ways.
Approximating the circumference with polygon perimeters is much simpler than approximating the circle area with polygon areas as Antiphon suggested. Using $96$-gons, Archimedes obtained what is now presented as the double estimate $3\frac{10}{71}<\pi<3\frac17$, although to Archimedes $\pi$ was not a number, and the result was phrased geometrically in terms of ratios of magnitudes. In 17th century Huygens refined the method further, and obtained the most accurate estimates to date, but after that analytic methods became more effective.
However, ancient Greeks also had a different concept of calculation, a purely geometric one, that was dominant in their time. A geometric magnitude was considered "calculated" if one could give a geometric construction for it. In the case of $\pi$ this meant constructing a square with area equal to the area of a given circle (or, after Archimedes, a segment with the length equal to half the circle's circumference). With straightedge and compass this is impossible (but it was only shown by Lindeman in 19th century), but Greeks also entertained more broad notions of "construction".
In this broader sense, the circle was first squared by Dinostratus around 350 BC using a curve, now known as the quadratrix. The curve itself was invented a century earlier by Hippias, who generated it by combining uniform linear and circular motions, and used it for angle trisection. In modern terms, from a segment of length $1$ it produces ("calculates") a segment of length $2/\pi$, and from that it is a simple matter to get a segment of length $\pi$ with straightedge and compass. Later Archimedes "calculated" $\pi$ in the same spirit using another curve generated by uniform linear and circular motions, the Archimedean spiral.
Comment: I would interpret it as the first algorithm what could - at least, theoretically - calculate $\pi$ with any precision.
Comment: Great point about the ultimate incalculability of transcendental numbers!
Answer: What do you mean "correctly or not"?
Here is a brief history. The Bible has a sentence which can be interpreted as implying that $\pi=3$.
The EXISTENCE of $\pi$ (the ratio of circumference to diameter) was rigorously proved by Archimedes. He also calculated it approximately.
For many centuries it was called the "Archimedes number".
As centuries passed, they calculated it with larger and larger precision. Today it is known
to more than a billion decimal digits and more. In 1990-th there was an interesting article in New Yorker magazine about the brothers Chudnovskii who evaluated the first billion digits. (With a huge computer they specially assembled for this purpose).
$\pi$ is a transcendental number, so you cannot "evaluate" it exactly (there is no finite or periodic decimal (or other) expression). This was proved by Lindemann in 1882.
Remark.
Let me also add that there was a crank in 19-th century who "proved" that $\pi=4$.
I think this is recorded in the Guinness book of records as the LEAST precise value of $\pi$ ever proposed. He offered his work as a gift to the State of Indiana. Indiana parliament had to
decide whether to accept the gift. They could not decide. The decision was postponed.
It is still postponed.
This gives some evil (or not informed) people a reason to say that "Indiana parliament
LEGISLATED that $\pi=4$". Don't believe these people.
EDIT: My mistake: certainly "existence of $\pi$" was known to Euclid. Conifold: thanks for the correction. To address the same remark of Conifold: Euclid and Archimedes (and possibly Eudoxus) certainly understood perfectly what is a "real number" though they used somewhat different terminology of "proportions". Theory of proportions of Euclid is equivalent to the theory of real numbers.
Comment: Archimedes did not prove the "existence" of $\pi$, to him it was not even a number. He phrased his results in terms of ratios of magnitudes as did all other Greek geometers. Even if we modernize Greek ratios into "numbers" the "proof" is already in Euclid's Elements, and is usually attributed to Eudoxus http://aleph0.clarku.edu/~djoyce/java/elements/bookXII/propXII2.html Cruder estimates in terms of inscribed/circumscribed polygons were also done before Archimedes.
Comment: For some amusement: https://en.wikipedia.org/wiki/Indiana_Pi_Bill, http://www.agecon.purdue.edu/crd/Localgov/Second%20Level%20pages/indiana_pi_bill.htm, http://www.agecon.purdue.edu/crd/Localgov/Second%20Level%20pages/Indiana_Pi_Story.htm
Comment: Alexandre Eremenko, @HDE226868 , do you guys know of other attempts besides Indiana Pi Bill? [Indiana Pi Bill: Other attempts to establish mathematical truth by legislative fiat?](https://hsm.stackexchange.com/questions/7347/)
Comment: Your presentation of the Indiana Pie bill isn't quite correct. The House actually passed it; the Senate is the one that blocked it, after some educative work in the background by concerned intellectuals and a lot of public backlash/mockery in the press.
Answer: Since the question specifically says "to any accuracy," I will assume you mean approximations as well.
In this case, the first recorded approximation of $\pi$ comes from the Babylonians, who not only had an awareness of it as being a specific constant, had approximated it's value to $3\frac{1}{8}$ or $3.125$. This is recorded in a tablet fond near Susa dating from 2000 BC.
Both the Egyptians and Archimedes had a value for it but these date from much later.
From the Rhind Papyrus dating from around 1650 BC we find an Egyptian's scribe method for obtaining the area of a circle which is equivalent to using the value  $\pi = 3\frac{1}{6}$ or $3.166$ repeating. This is perhaps nearly as good as the Babylonian approximation, but the Egyptians did not apparently have an awareness of it as being a specific constant, this is merely the effective value of it arising from their method.
From Archimedes there is given an approximation of $\pi$ more accurate than either the Egyptian or Babylonian, but this dates from almost 2000 years after the recorded Babylonian value.
Comment: Well, it's your question, but you did specifically ask about Archimedes vs Babylon vs Egypt and Conifold left out the Babylonians even though they had an approximation nearly a Millenia before Archimedes or Antiphon or Eudoxus or any other Greeks. Indeed, the mathematical center of the world was at one point, Babylon. After that, it shifts slowly to Egypt, and after that, Greece and the Mediterranean. The top voted answer neglected two whole periods, I felt.
Comment: You're a little late to the party... Conifold's answer is good enough
Answer: There is a terrific summary here which includes the degree of accuracy with chronology, if that is what you are interested in.
Pre computer calculations of π
Mathematician           Date     Places Comments
1   Rhind papyrus       2000 BC  1      3.16045 (= 4(8/9)2)
2   Archimedes          250 BC   3      3.1418 (average of the bounds)
3   Vitruvius           20 BC    1      3.125 (= 25/8)
4   Chang Hong          130      1      3.1622 (= √10)
5   Ptolemy             150      3      3.14166
6   Wang Fan            250      1      3.155555 (= 142/45)
7   Liu Hui             263      5      3.14159
8   Zu Chongzhi         480      7      3.141592920 (= 355/113)
9   Aryabhata           499      4      3.1416 (= 62832/20000)
10  Brahmagupta         640      1      3.1622 (= √10)
11  Al-Khwarizmi        800      4      3.1416
12  Fibonacci           1220     3      3.141818
13  Madhava             1400    11      3.14159265359
14  Al-Kashi            1430    14      3.14159265358979
15  Otho                1573     6      3.1415929
16  Viète               1593     9      3.1415926536
17  Romanus             1593    15      3.141592653589793
18  Ludolph Van Ceulen  1596    20      3.14159265358979323846
19  Ludolph Van Ceulen  1596    35      3.1415926535897932384626433832795029
20  Newton              1665    16      3.1415926535897932
21  Sharp               1699    71
22  Seki Kowa           1700    10
23  Kamata              1730    25
24  Machin              1706    100
25  De Lagny            1719    127     Only 112 correct
26  Takebe              1723    41
27  Matsunaga           1739    50
28  von Vega            1794    140     Only 136 correct
29  Rutherford          1824    208     Only 152 correct
30  Strassnitzky        1844    200
31  Clausen             1847    248
32  Lehmann             1853    261
33  Rutherford          1853    440
34  Shanks              1874    707     Only 527 correct
35  Ferguson            1946    620

Computer calculations of π
Mathematician        Date      Places   Type of computer
Ferguson            1947       710      Desk calculator
Ferguson, Wrench    1947       808      Desk calculator
Smith, Wrench       1949      1120      Desk calculator
Reitwiesner et al.  1949      2037      ENIAC
Nicholson, Jeenel   1954      3092      NORAC
Felton              1957      7480      PEGASUS
Genuys  Jan         1958     10000      IBM 704
Felton  May         1958     10021      PEGASUS
Guilloud            1959     16167      IBM 704
Shanks, Wrench      1961    100265      IBM 7090
Guilloud, Filliatre 1966    250000      IBM 7030
Guilloud, Dichampt  1967    500000      CDC 6600
Guilloud, Bouyer    1973    1001250     CDC 7600
Miyoshi, Kanada     1981    2000036     FACOM M-200
Guilloud            1982    2000050
Tamura              1982    2097144     MELCOM 900II
Tamura, Kanada      1982    4194288     HITACHI M-280H
Tamura, Kanada      1982    8388576     HITACHI M-280H
Kanada, Yoshino,
Tamura              1982    16777206    HITACHI M-280H
Ushiro, Kanada      1983    10013395    HITACHI S-810/20
Gosper              1985    17526200    SYMBOLICS 3670
Bailey  Jan         1986    29360111    CRAY-2
Kanada, Tamura      1986    33554414    HITACHI S-810/20
Kanada, Tamura      1986    67108839    HITACHI S-810/20
Kanada, Tamura,
Kubo                1987    134217700   NEC SX-2
Kanada, Tamura      1988    201326551   HITACHI S-820/80
Chudnovskys         1989    480000000
Chudnovskys         1989    525229270
Kanada, Tamura      1989    536870898
Chudnovskys         1989    1011196691
Kanada, Tamura      1989    1073741799
Chudnovskys         1991    2260000000
Chudnovskys         1994    4044000000
Kanada, Tamura      1995    3221225466
Kanada              1995    4294967286
Kanada              1995    6442450938
Kanada, Takahashi   1997    51539600000     HITACHI SR2201
Kanada, Takahashi   1999    206158430000    HITACHI SR

Who was the first to calculate $\pi$?


SSH freezing randomly

Question: I use PuTTY to control my pi a lot.  Normally it works fine, but as of a few days ago my main computer will just stop receiving data from my pi and freeze, and I have to close PuTTY and open a new session, meaning that I lose connection with what I've been doing earlier.  Sometimes it will do this on start-up and I can't connect until I reboot my pi manually(pulling the plug out).  Any Suggestions?
Comment: Have you started doing more with GPIOs or added something new to the USB? I had this happen when I slightly overdrew the power.
Comment: You should indicate the pi model and OS you are using; I am presuming Raspbian (but I think this will apply to most others): Try `grep "oom-killer" /var/log/syslog` and if anything comes out with a timestamp in the window of your problem, edit it into your post.
Comment: Do you have a serial cable or a display or something plugged in? You should check if the pi hangs or crashes or if it just loses its network connection.
Answer: I experienced a similar issue. It seemed that if executing a command over ssh that returned more than a few lines that ssh would freeze. sudo apt-get upgrade would run fine, but ls -r or ifconfig would freeze after about 10 lines. Changing the MTU settings resolved the issue for me.
The following command resolved things. I was connected over wifi, so replace the interface name as necessary. Default MTU was 1500:
sudo ifconfig wlan0 mtu 500 up

Comment: Worked for me on jessie
Answer: Is the Pi connected via Wifi and a USB ethernet adaptor? You may find the USB Wifi NIC is going to sleep, I edited /etc/modprobe.d/8192cu.conf and added
options 8192cu rtw_power_mgnt=0 rtw_enusbss=0

and it solved the problem for me but this info depends on the chipset, I'm using the Edimax USB wifi adaptors so you may have to search for the solution for your chipset.
Comment: Is this wheezy?  File doesn't exist in Jessie.
Answer: This is not an answer to avoid freezing but about keeping the session running and available if ssh connection is lost:
You can try tmux (or screen) they are meant for that:
tmux allows one to switch easily between several programs in one terminal, detach them (they keep running in the background) and reattach them to a different terminal. And do a lot more.
Connect to the pi:
ssh pi@raspberrypi

Launch tmux:
tmux

You can now work safely.
In case you get disconnected for any reason, you can log back:
ssh pi@raspberrypi

List the running tmux sessions:
tmux ls

This should display the list of open tmux sessions. Example:
0: 1 windows (created Sun Jul  5 12:05:35 2015) [80x23]
1: 1 windows (created Sun Jul  5 12:05:44 2015) [80x23]

You can than select the desired session with the attach command:
tmux -t 1

Answer: For me the problem was this:
https://www.raspberrypi.org/forums/viewtopic.php?f=91&t=122601
So after commenting out this chunk of /etc/rsyslog.conf the Pi is not doing unexpected rebootings anymore (which caused the broken pipe ssh freeze):
daemon.*;mail.*;\
       news.err;\
       *.=debug;*.=info;\
       *.=notice;*.=warn       |/dev/xconsole

SSH freezing randomly


Script to reorder ACLs in Windows server 2008?

Question: I have ran a tool called admnalow.exe that re-grants access to the local administrators (BUILTIN\Administrators) group for all directories and subdirectories in a given path.  The problem is it seems to have caused the ACL's to be ordered improperly.  I've been looking everywhere and have been unable to find a .vbs or any other script that will parse through a set of directories and reorder the ACLs.  This can be done manually but would be incomprehensible for thousands of directories.
Can anyone help?!?!
Answer: The built-in icacls command with the /verify argument will do what you're looking for. Add the /T argument to make it apply to files and subdirectories.


Dealing with the "diversity question" answer

Question: The question How to answer the diversity question during faculty interview has attracted a few answers, but one in particular stands out as being both rather non-politically correct and also quite accurate. I'm curious if/how the community wishes to deal with this particular. It's already had a few flags raised (rude/abusive, not an answer). I'll post my own thoughts in an answer below.
Comment: "and also quite accurate" - clearly debatable.
Comment: @henning--reinstateMonica: That's certainly not the intended or stated purpose by most of its proponents, but there's a reasonable argument that that's an ulterior social goal/effect.  Compare an argument like "the purpose of the American two-party system is to block real change and maintain the dominance of the political elite".  I don't *agree* with the answer's argument, but I think it's in the realm of "reasonable but debatable claim" rather than "outright falsehood".
Comment: "Understand that the above question is to weed-out individuals who do not lean as those in power lean." That's certainly not accurate.
Comment: Do we have any analysis of who upvoted the answer?
Comment: @DJClayworth - Nope.
Answer: I think it's likely that the voting on this particular Q&A has been tilted by exposure to the Hot Network Questions, and the answer is by someone who hasn't participated on Academia.SE before. I have a bit of doubt that the answer is supported by any particular experience of the answerer, and instead is based on their biased view of what academia is and what academic hires involve.
It really seems like "HNQ bait" to me, rather than an answer meant to be helpful to the OP. I think it distracts from other answers that help OP to understand what is meant by these sorts of questions.
That said, I think it's difficult to moderate this sort of answer. I've downvoted it, and upvoted the other answers I think are actually helpful. I think that's all we can really do.
Comment: Didn't even realize that this was an HNQ. *sigh* That feature is one of the least useful and most damaging elements of the whole SE network.
Comment: You're certainly right, but you wouldn't believe how many academics I met in my life who would give answers that look like "answers by someone who hasn't participated on Academia.SE"
Comment: @BryanKrause Wow, really? How does the HNQ algorithm work? Can the mods tinker with it so that we don't have to wade through the same idiotic nonsense every time someone says "diversity"?
Comment: @ElizabethHenning We can remove questions from the HNQ list, and that has been removed, and there's also a [chat](https://chat.stackexchange.com/rooms/92757/the-outreach-department) that list the HNQ questions from this site, but we cannot foresee whether a question will become really problematic or not. See also [this post](https://academia.meta.stackexchange.com/q/4454/20058) and [this one](https://academia.meta.stackexchange.com/q/4483/20058).
Comment: @eykanal Eh, I don't know if I agree with "least useful" - it certainly helps people discover other parts of the network, and there was massive uproar when a certain site was excluded from the HNQ. But "most damaging" - yes, it certainly can be when the wrong questions get there. Might be worth another entry at https://academia.meta.stackexchange.com/questions/4454/moderators-can-now-exclude-questions-from-the-hnq-list-when-should-we-use-this
Comment: While I don't know anything about the poster of the answer, the question described is applicable to workplaces other than academia, so any of knowledge about academia shouldn't be seen as a disqualifying fault.
Comment: @MassimoOrtolano Oh I would believe it, just speaking about this particular answer and the information available around it.
Comment: @eykanal If you look at the HNQ chat feed, you can see that this particular question had a single vote when it hit HNQ.
Comment: @ElizabethHenning There are probably some details on MSE somewhere you can dig up. The threshold is based on the level of activity on the site, so smaller sites can more easily hit the HNQ. Questions getting multiple answers shortly after being posted is one cause.
Comment: @MassimoOrtolano and Bryan Krause: Thanks for the info. The HNQ chat feed is an excellent idea, this is the first I've heard of it.
Answer: The OP's post talks about "how" questions posed in the interview. "How" do you support X. That implies that the decision is already been made that X should be supported.
In that sense, the controversial answer and eykanal's suggested version are both not really answers to the "how", or to the "what aspects" questions of the OP.
That doesn't make paulj's answer untrue; it is a political issue. Society put a political question to the university ("what are you going to do about diversity"). Whatever response the university gives is political. To do something about diversity is political; to not do something is also political.
I think that with cag51's edits that removed some incendiary language, the answer as it stands now represents a reasonable perspective. (Even if I don't really agree with the undertone.)
Comment: Yeah I don't think it's a very helpful answer since it doesn't give advice on how to do well in the interview. But it succinctly informs on why you can't just stay quiet when asked those questions, and that questioning the premises of those questions is not going to work well. So it's not entirely without merit.
Comment: @TannerSwett what universities should or shouldn't do about diversity is "political" because it's a political matter in society right now, and universities have a quite central position in public debate.
Comment: +1 The answer we are discussing doesn't actually provide any suggestions as to what to say in the interview, which was what the question asked.
Comment: The question is not political. But the answer we are discussing is unquestionably political.
Comment: I'm not disagreeing with you, but to be a decent answer there needs to be some actual suggestions of what to say in answer to the question.
Comment: What do you mean by "political," exactly? I don't see anything political about the question "what will faculty do about diversity"; it's not a question about policy or government.
Comment: +1... I like the nuance here. That said, I'm not sure everyone reads this question the same way. I definitely read "how" as "what are my options in answers?"
Answer: At the moment I'm writing this, it is the highest voted answer. To me, that's the community's answer.
Deciding what to do about it in meta, is not what "the community wants" but rather what a the much smaller group who frequents meta wants.
Comment: I disagree that it's necessarily the "community's answer" depending on the definition of community - this question has been on the HNQ which tends to bring in voters from around the network that might not have any involvement with academia. That outside community might upvote sentiments that reflect their assumptions about what academia is and enjoy a bit of a controversial answer.
Comment: @MartinArgerami Users without rep on Academia can only upvote. Downvotes are gated by rep (and the 100 association bonus for rep on another site is not sufficient for downvoting privileges).
Comment: Well, the opposite could be true, right? Maybe all the downvotes come from those outside Academia. And in any case those outsiders still can vote here in meta. My point is that the meta question is choosing a subset of users to decide on the question, and it is not obvious to me why that would be fair.
Comment: But people can upvote as many answers as they want, so I don't  clearly see where the split would happen.
Comment: Unfortunately quip answers that don't explain much but agree with the voters' biases are quite common, esp. on politics SE. Since they often get posted first they tend to get a lot of votes in HNQ, even if they impart little information but a lot of opinion. It says more about the nature of SX (and HNQ in particular).. https://meta.stackexchange.com/questions/9731/fastest-gun-in-the-west-problem
Comment: I'm not sure about it - several of the other answers have common ground, so votes may be split among similar answers.
Comment: They can, but we can't see if they do. For example if people voted only the first time they saw the issue and didn't come back to read newer answers.
Comment: At least one downvote came from Academia.
Answer: The answer is honestly quite accurate, but uses unnecessarily opinionated language. I would prefer if the answer would be simply factual, possibly as follows:

This question has only one correct answer, unfortunately. Providing anything other than a positive "I support diversity through <methods>" is likely to significantly harm your application.

The above says the same thing as the current answer but without the attitude.
Comment: @DanRomik - My take is somewhat different than Massimo's; you can have all the attitude you want, but don't bring it here. This is a forum strangers to talk to each other. No one knows each other. Bringing unnecessary attitude is a great way to  tick off someone with little added benefit. On this site, I'm all about the boring.
Comment: There's enough people in the US running around in red ball caps to convince me that sometimes what people believe to be true is not true.
Comment: Are we so fragile that we cannot tolerate a bit of what you call "attitude" (and I'd call "personality") in an answer? I'd argue that this so-called attitude is precisely the reason the answer got so many more upvotes than other answers that say similar things but in the kind of bland, boring language you are advocating for. So, respectfully, when you say "_the above says the same thing as the current answer but without the attitude_", to me that comes across as saying something _flattering_ about paulj's answer and unflattering about your suggested language, rather than the other way around.
Comment: @DanRomik In the "analog" life, as everyone around me knows well, I'm the opposite of fragile. Whenever I speak in public or with some authority everyone is scared by what I can say (friends say that I suffer from "excess of personality"). But here, as a moderator, I find it difficult to deal with answers like that. Look at the timeline and see how many flags that answer already received; as a moderator, you can: i) continue to decline flags; ii) ignore the flags, but after 6 rude/abusive flags the answer gets deleted automatically; iii) try to edit the answer to make it less controversial.
Comment: What evidence can you (or, more appropriately, the answerer) point to to confirm it's veracity.  If that info were provided in the answer, it would be a valuable answer, and not a "look how PC the process is" rant.
Comment: @ScottSeidman - addressed in my comment on your answer.
Comment: Not to mention the problem of moderating comments. There are clear limits in the SE platform that make it fragile with respect to certain questions or answers.
Comment: @MassimoOrtolano thanks for interesting perspective re: moderation. Well, yeah, sure, if you need to moderate, give it your best shot and I appreciate your efforts and am fine with whatever decision you make. But if you declined the flags initially then it sounds like you agree the answer deserves to stay, so declining more flags seems like a reasonable solution. Anyway, FWIW, count me as one community member who thinks this answer is no worse than many others and should be left up for people to judge on its merits, or lack thereof.
Comment: "only one correct answer" only to extent that if you wholeheartedly disagree with the University's policy you probably won't get hired. What that policy is might actually vary; there were [even] some openly pro-Trump colleges, but those would probably not be asking the "how" question. I mean your answer and paulj's are basically just saying "be a yes-man on this".
Answer: The answer is actually not an answer to the question. The question asks about what to say in response to the interview question. It specifically says "Which aspects [do] I need to cover to delivering a winning answer?"
The answer does not address that issue at all. It presumes the questioner is really asking about whether diversity is 'valid", and merely provides political commentary on whether they should go along with it or not.
We respond to this by downvoting. Also by upvoting the much better answers that there are to the question.
Let us also take not of the fact that writing this answer is the user's ONLY activity on Academia. It's a drive-by answer.
Comment: I didn't downvote, but I disagree with your take. "You should say what the interviewer wants to hear" seems to me an acceptable answer to the question.
Comment: In the abstract, sure. The tough part is that usually you don't know what the interviewer wants to hear. In this case, though, the answer is known, and the penalty for answering wrong is the legal dept calling "risk!" and you not getting a job.
Comment: Please upvote or downvote only on the merits of the answer itself, not on the credentials of its author.
Comment: @ScottSeidman - My comment on your answer addresses your points.
Comment: Why do we all jump to the conclusion that the question is being asked because the OP has objections to the "diversity" issue? The question gives no indication that they know what a good answer sounds like, and every indication that is what they are asking. The answer to every question about interviews is "You should say what the interviewer wants to hear".
Comment: @eykanal  I would have no issue with the answer "You should say what the interviewer want's to hear."  That's not how the answer is worded.
Comment: And the reason for the downvote?
Comment: Why do you think the answer is known? I see people on this site jumping to the conclusion that the questioner is complaining about politics rather than actually wanting an answer to the question they asked.
Comment: @eykanal -- have you been involved in such decisions, and can say that you know this happens?  Can you point us to Inside Higher Ed articles that say it happens?  Can you point us to a candidate that feels this happened to them?
Comment: My take is that the implied undertone is "This is what you should say to get the job." (so it's an answer) followed by "You should consider whether you _want_ the job when the question is asked".
Answer: Imagine an answer to an analogous question on Workplace SE saying that if you attack the hiring manager's priorities or you criticize the stated organizational goals, you won't get the job. Well, duh. Why should they hire someone contemptuous of what they're trying to accomplish?
I'm pretty sure such an answer wouldn't do very well on Workplace SE. The difference here is that a lot more people think their uninformed opinions about academia are worth something. Also, the answer score may have been affected by the users that drift in from the HNQ. Just downvote.
Comment: This answer has attracted a significant number of rude/abusive flags (ironically, a similar situation to the post this meta question is discussing!). I've taken a stab at editing the answer to remove some of controversial language while trying to keep the spirit of the answer intact.
Answer: Why are you so sure it's correct?  Does the answerer provide any data suggesting that people who have a poor answer to such questions don't get hired?  Have they sat on a search committee that eliminated a candidate based on this factor?  This is anecdotal at best, and wrong at worst.
Then again, I suppose "I have no commitment to promoting diversity, and my actions will be counter to such efforts" would be a fine reason to not hire someone onto a campus committed to a diverse student body.  I'm curious about whether "I haven't considered diversity issues" would eliminate a candidate, but until the answerer can provide some background establishing credibility, I have no reason to believe that the answerer has any more insight that I might.
Note that in the sense that the answer does not answer the asker's question, it's not a real answer.  It's a rant.
In any case, I suggest it doesn't meet the "be nice" standard, as there are much less offensive ways to say the same thing, and the answerer hasn't even tried to phrase this nicely.  I don't care if I'm personally offended, but there is a community standard, in writing.  I may or may not agree with it, but via my participation, I signed on to it, and if I didn't want to adhere to that standard, I would stop participating.
Comment: I'm sure for the same reason I'm willing to post answers to *any* question on this site... I've seen this same thing so many times that I'm comfortable stating it's a solid pattern by now. I have seen people get rejected for position on this basis, and I've seen people with comfortable jobs get fired for violating the spirit of the question. So yes... personally, I'm pretty confident that this "correct".
Comment: So, you've been in the room with a search committee, and you've heard "this is an absolutely outstanding candidate, except for that unfortunate answer to the diversity question, so we can't hire them"?  If so, I stand corrected.  I'm curious about the terminations you mention, and can sort of see that -- though usually as a result of public statements that counter a universities standards.  I'm having a hard time figuring out if I put those in the same basket.
Comment: Your claim of credibility  by virtue of experience probably belongs in your answer.  It makes it seem less anecdotal


How to create an effect like in the below picture?

Question: I would like to know what kind of effect/filter applied in the below image (from an online shopping website) to look in this way. I'm a newbie to photo editing.

Your help is greatly appreciated.
Thanks !
Comment: Welcome to **GD.SE** - please take a look around at [tour] to learn about our community - also read [ask] and [answer] a question to learn what makes a good query here and how best to frame one. This looks like a basic HDR shot of a place with coloured paint over stones - I don't see any special "effect" besides HDR - what am I missing? Also, what have you tried?
Comment: Possible Duplicate: https://graphicdesign.stackexchange.com/questions/26124/how-can-i-get-this-hdr-or-painted-blur-effect-from-a-photo
Comment: Possible duplicate of [How can I get this HDR or painted blur effect from a photo?](https://graphicdesign.stackexchange.com/questions/26124/how-can-i-get-this-hdr-or-painted-blur-effect-from-a-photo)
Answer: The place you need to start exploring is HDRI images, and more specific, Tone mapping. Tone mapping is a step on the so-called "HDRI look". This increases the contrast of an image, but in a different way, that normal contrast does.
Normal contrast adjusts all the image in "a single pass"; the modification is applied to all the image; where Tone mapping analyzes zones, for examples the sky, which is on the bright side of the histogram on the image and applies one contrast on that zone. And analyzes a different zone, the stone building, and applies contrast there.
Remember that amplifying contrast also saturates more an image as a side effect, so the overall saturation can be a byproduct of the Tone Mapping.

That is on the "Photo editing" part. You can do Tone mapping on a single image, preferably starting from a raw image, but you also can stack several bracketed images to exploit the light from the original scene.
Take a look at this paper I made a while ago.
Answer: (Your question is a bit difficult to understand but here is my answer.)If you want to enhance your photos i suggest messing around with the threshold,colors and hue-saturation menu to bring out certain colors within the image.(Since I use gimp these are my suggestions for GIMP) Also i don't recognize any filters used in this picture.. It seems like a good camera to me.(Maybe they sharpened the image then adjusted the brightness. After that they could have selected certain colors within the Hue saturation and edited them to choose what colors should stand out the most.
Answer: In Photoshop add a hue and saturation adjustment layer and click on colorize. For the first part of the image you want to change, select the desired hue and other settings. At first the entire image will change. Now invert the mask color from white to black by selecting it, then hold down Comm on Mac or Control on PC and clicking on the mask. Now with a black mask, select a white brush with a soft edge and start painting on the parts to change. Then try different Layer Blend Modes. Repeat with new Hue and saturation adjustment layers with new settings.


A word for someone who is unwanted, a pariah, someone left to fend on their own?

Question: I'm writing a book and I need a word to call a character who is punished for becoming part of a group of people who are socially rejected and unwanted. They are left to fend for themselves on the street.
Answer: It looks like you already have one.  "Pariah".
If you're looking for a similar word with less of the specific connotations of 'Pariah', then the word 'outcast' would probably suit your needs.
One who is forbidden from a group out of shame could also be said to be "banished" from the group.
Comment: also "shunned".
Comment: Also "sent to Coventry": http://www.phrases.org.uk/meanings/sent-to-coventry.html
Answer: You might want to use ostracized, it fits perfectly:

ostracize, ostracise [ˈɒstrəˌsaɪz] vb (tr)
  1. to exclude or banish (a person) from a particular group, society, etc.
  2. (Historical Terms) (in ancient Greece) to punish by temporary exile
[from Greek ostrakizein to select someone for banishment by voting on
  potsherds; see ostracon]
Answer: One particular term for individuals who are outcasts is untouchable, used as a noun.

a member of the lowest-caste Hindu group or a person outside the caste system, contact with whom is traditionally held to defile members of higher castes.

While often applied to the Dalit community in South Asia, this term is used for various groups in other countries as well.  See discussion here.
Answer: Please consider:

outcast 1: one that is cast out or refused acceptance (as by society) : pariah

from m-w.com
Comment: This is almost too obvious to post, since in m-w "pariah" mentions "outcast" in the 2nd definition.
Answer: Leper would work. Note the 2nd definition from M-W:
Definition of LEPER
1
: a person affected with leprosy
2
: a person shunned for moral or social reasons
You could also describe the character as a social leper.
Answer: "Untouchable" was one of the suggestions, and it fits nicely, especially with ethnic connotations.
On the other hand, "untouchable" can also have a nearly opposite meaning, someone or something that cannot be equaled, especially in a competitive setting.  It was also the nickname of group of Federal agents in the US because they were not susceptible to graft.
It's all in the context.
Answer: An interloper is a person who becomes involved in a place or situation where they are not wanted or are considered not to belong.


Conditional formatting based on number of characters

Question: In Google Spreadsheets, is there a way to conditionally format a cell if it has more than 30 characters?
Answer: Yes! Highlight the cells you want to format. Go to Format > Conditional Formatting.
Once you're in the conditional formatting dialog, choose "Custom Formula Is" from the select box (it's the last option). In the text field type:
=len(XY)>30

X will be the column you're in and Y will be the row you want it to start at. So if you want to check the entire column A starting at row 4, your formula would look like this:
=len(A4)>30

Then just assign a background color/text color. If you have selected an entire row, you will need to adjust the range if you've got a couple of heading cells. In my case, I selected the entire column but I only wanted to check starting at A4 and continuing to the last row in the column. In this example, the range then should be A4:A.
Here's a screenshot of what I had:

And here's how the data looks after clicking "save rules":

I added a second column in there that counts the length of the string. That was just as simple as highlighting the column and adding a function to each cell:
=LEN(A1)

Hope that helps!
Comment: Don't forget the = at the start of the custom formula. I was trying just "LEN($A1) > 10" and it wasn't working, until I put the equals sign in!
Answer: Not on the cell itself, without the usage of Google Apps Script. Adding a helper column will allow you get realy close:

A1 and A4 both have more than 30 characters. Set the whole column to have a conditional format like this:

Now add the following formula in B1:
=ARRAYFORMULA(LEN(FILTER(A:A;A:A<>""))>30)

This will check column A, whether the entry has more than 30 characters and will return TRUE or FALSE.
See example file I've prepared: more than 30 characters
Answer: To make sure you don't have to do this for each cell separately, you can play with the range function:
To format cell A1 if the length of the text in it is longer than 100 chars:
Google Sheets menu → Format → Conditional Formatting
=LEN(A1)>100         //or: =LEN(A1:A1)>100

In the range field:
A1:A1

Set the colour as you wish.
Simply pull the cell down to let this rule apply to other cells in column A!
Answer: If your cell is A1, in New Google Sheets, in Custom formula is please try:
=len(A1)>30 withRange: `A1` and the formatting of your choice.


Orange Import and process spectra time dependent/kinetics

Question: I would like to import FTIR spectra that have been collected over time then use Orange to preprocess these as a group. I currently have the spectra as individual SPC or CSV files. How do I import the spectra then plot them as a stack? I have tried using the "Multi-file' widget but that does not work.
Answer: To accomplish this, you can use the Orange Concatenate Widget under the Data tab shown below:

This widget takes a primary data set and an additional dataset and concatenates them into one dataset. Once all of your data points are contained in the same dataset, you should have no problem plotting them all together.


Using university's resources that are online

Question: A lot of the time when looking for information about a topic online I come across another university's resources that are publicly available. Some have a full listing of all the resources available for that course and others just have a PDF for one topic of the course. Can I read them or download them?
Comment: If they did not want you to have them, then you won't find them...
Comment: What are you concerned about?
Answer: It is fair to say that if someone publishes something on the net then you can download and use it freely for personal use just as if you check it out from the library. At least, I've never heard any opinion that would challenge that.
Beyond that, you have to consider a few things. In the US, at least, authors gain copyright (all rights) to anything they create. If you don't find another statement to the contrary, then you have to assume that "all rights are reserved." To use something for other than personal use, for example republishing it in any form, you need permission: a license.
Some web resources are explicitly licensed with the terms carefully stated, such as through Creative Commons. Some are explicitly stated to be "Public Domain". But in the absence of such statements, assume that all rights are reserved.
It is easy enough to ask educators for permission to use their materials and most will give you some sort of license to do so. But you can still plagiarize people even when you have a license.
But for academic resources there is another consideration. If you found it, so can your students. So, reusing found exams and homework questions can be a bit risky. You can safely mine the resources for "ideas" of course, as ideas are always free to use.
I would like to say that you can freely link to found resources, as that seems sensible to me, but there are laws, especially in EU, that are bringing that idea into question. It is unlikely that you would be challenged for linking to an academic site, though you could possibly be for linking to a news site. The world of copyright is a bit weird and getting worse.
In the not too recent past, "fair use" permitted some limited reuse of the work of others, but only for specific purposes (and with attribution). One of the fair uses was scholarship, but that has been going away ever since the Xerox machine was invented, with "content owners" working through governments to limit use more and more. The bigger problem is that the rules of "fair use" are too variable to make general statements about them. What is allowed in EU may be forbidden in US, for example.
Personal use: fine. Beyond that, look for a license, ask, or beware.
Answer: You can read and download them. They made them publicaly available so that students from their institute and other can read and download them.You may be worrying about the copyright crap. Don't worry about it, Just do what ever you want.
Comment: _Don't worry about the "copyright crap"_ is extremely poor advice.


Deleting large portions of shapefile

Question: I'm have a huge shapefile and I'm trying to delete large portions of it. I can't seems to do it in the edit mode. Can someone please walk me through this process? I'm using QGIS 1.8.
Comment: `"I can't seems to do it in the edit mode"` What do you mean?
Answer: Ah, figured it out. I had posted this question awhile back and got it answered. I haven't touched QGIS in awhile so it was a little fuzzy for me.
I couldn't do it when I toggled into editing mode. I realize that you have to go into edit mode, VIEW > SELECT > SELECT FEATURE BY ... and then hit the X button.

Deleting large portions of shapefile


WD smartware 1tb drive Unlock

Question: I have a drive where the usb on the chip broke and can not access the hard drive because of the smatware password.If i plug in hardrive I can re format, but how do i access the drive to recover my files before resetting the drive. i know my password, but cannot access the smatware software to unlock the drive any one have any ideas. WD says I have to go to datareceovery for over $400 dollars.
Answer: Try updating the firmware to remove the smartware altogether?
See this question: How do I remove a MyBook's "WD SmartWare" virtual CD from my desktop?
You can also give TestDisk a try, it's saved me many times for data recovery purposes but may also be able to read past the smartware lock.

WD smartware 1tb drive Unlock


How to deal with VBOs when rendering mesh's that may or may not be displayed?

Question: I'm working on a multiplayer game and will be displaying other players near the player.  At most 16 players could be near the gamer however there could also be 0.  What I'm thinking of doing is setting up 16 empty VBOs so they're ready to load with character's position when the client receives them.  Is it valid to create empty VBOs?  If not how should I go about rendering data that may or may not be there depending on what the server is sending the client?
Comment: I see no reason why you would need 16 pre-allocated VBOs. Why not have a list or something with PlayerObjects (which inherits your Drawable interface and has a VBO member) or something that represent the 16 nearest players and handle it in an OO fashion?
Answer: The thing you seem to be missing is the concept of transforming objects. A mesh doesn't have a position in the world; it's just a collection of vertex data. When you render the mesh, you transform that vertex data from its default location to a place in the world.
This is what all of that matrix stuff people use does; vertex positions can be transformed by transformation matrices. Vertex shaders are primarily responsible for this.
This means that you don't modify the vertex data on the CPU. You don't translate it yourself; you let the GPU do the translations. When you render an object, you provide a transformation to the GPU, and your vertex shader will apply it.
Answer: This is obviusly bad approach. By creating empty VBO you will not gain any extra  performance and you will waste memory.
So from the rendering point of view:

If you wanna save memory: Create VBO per object if it is visible. If it is not visible, release it. But i do not recommend this for a simple game, since you are slowing game down.
If you wanna be fast: Just have VBO per object and do not render it if it is not visible.
If you wanna be super fast: Have all objects in one long VBO and render it using offset.
Answer: First, make a list of the resources (VBO, Texture, Shader, etc.)  the current map/level needs to be rendered.
Second, compute the amount of memory each resource consumes.
If everything fits in GPU memory, simply copy everything and render. If it doesn't fit, you'll have to devise a caching system.
Keep often used resources in GPU memory. Release unused resources when they're offscreen (and quite far from the current view). If rendering a single frame requires more memory than available, the process will be harder and quite slow.
To render only what's shown, you need a list of renderable "objects" along with their position and, maybe, their bounding volume. Keep a camera frustum updated in your game code and cull objects against it. Then, build a list of objects to render and send those to your renderer.
OpenGL will allow you to render objects, but you still need to build a minimal framework to identify what you want it to render. If your game is very simple, a simple distance test might be enough instead of frustum culling.


Relative quaternion to global with uncertainty

Question: in this perfect tutorial i found how i can compose two poses with uncertainty and how i can transform one representation to another with uncertainty  http://ingmec.ual.es/~jlblanco/papers/jlblanco2010geometry3D_techrep.pdf.
Let's suppose I have one global point which represent 6 dof and 6 confidence and another one also representing by 6 dof and 6 confidence. How can I get "mean" point with uncertainty.
Answer: The tutorial you linked is a good one but does not deal with the uncertainty well. Unfortunately, what @tuskiomi suggested is for euclidian space variable with single-dimension. Following is a better way of doing your problem. Although it is two poses example, it can be extended to more poses easily.
Fusing multiple observations of a pose.
\begin{equation}
p(\textbf{z} | \textbf{x}) = \prod_{i=1}^{k} p(\textbf{z}_i | \textbf{x})
\end{equation}
Two observation example
\begin{equation}
ln(p(\textbf{z} | \textbf{x}))=ln(p(\textbf{z}_1 | \textbf{x})p(\textbf{z}_2 | \textbf{x}))
\end{equation}
\begin{equation}
ln(p(\textbf{z} | \textbf{x}))=c(\textbf{x}^T\Sigma^{-1}\textbf{x}-2\textbf{x}^T\Sigma^{-1}\textbf{z}+\textbf{z}^T\Sigma^{-1}\textbf{z})
\end{equation}
\begin{equation}
\begin{split}
ln(p(\textbf{z}_1 | \textbf{x})p(\textbf{z}_2 | \textbf{x}))&=c(\textbf{x}^T\Sigma_1^{-1}\textbf{x}-2\textbf{x}^T\Sigma_1^{-1}\textbf{z}_1+\textbf{z}_1^T\Sigma_1^{-1}\textbf{z}_1+\\
&\textbf{x}^T\Sigma_2^{-1}\textbf{x}-2\textbf{x}^T\Sigma_2^{-1}\textbf{z}_2+\textbf{z}_2^T\Sigma_2^{-1}\textbf{z}_2)
\end{split}
\end{equation}
Here is your new uncertainty
\begin{equation}
\begin{split}
\textbf{x}^T\Sigma^{-1}\textbf{x}=\textbf{x}^T(\Sigma_1^{-1}+\Sigma_2^{-1})\textbf{x}
\end{split}
\end{equation}
\begin{equation}
\Sigma=(\Sigma_1^{-1}+\Sigma_2^{-1})^{-1}
\end{equation}
and mean.
\begin{equation}
\begin{split}
\textbf{x}^T\Sigma^{-1}\textbf{z}=\textbf{x}^T(\Sigma_1^{-1}\textbf{z}_1+\Sigma_2^{-1}\textbf{z}_2)
\end{split}
\end{equation}
\begin{equation}
\textbf{z}=\Sigma(\Sigma_1^{-1}\textbf{z}_1+\Sigma_2^{-1}\textbf{z}_2)
\end{equation}
It might work but occasionally it will suffer from the singularity problem.
The proper way of doing this is fusing them on manifold. If you want to learn more about uncertainty fusion of SE3 poses you should read State estimation for robotics by Prof. Tim Barfoot.
Comment: @tuskiomi I am not sure because I have no idea what is convolution in probability. In robotics, this is usually called Bayesian fusion or recursive fusion or MAP estimation.
Comment: https://web.kamihq.com/web/viewer.html?file=http%3A%2F%2Fwww.tina-vision.net%2Fdocs%2Fmemos%2F2003-003.pdf&source=extension_open_button i found similar solution in this book. But I also need update a new pose iterative.  For this problem I can use The Convolution of Two Univariate Gaussian PDFs, isn't it? And one more question, does it work for SE3 matrix or quaternion?
Comment: Not sure about the convolution. I am not sure if you need that. To iteratively update your final pose with a new pose, you just need to iterate the two pose fusion above which is referred to as a recursive estimation. As I mentioned that will fail occasionally. I strongly recommend using SE3 pose fusion. Have a look at the section V.A of my paper: https://arxiv.org/pdf/1901.07660.pdf I did exactly the same thing you mentioned.
Comment: now correct me if I'm wrong, but this solution is the result of convoluding many distributions together correct?
Answer: This is more of a statistics question. Convolude 2 normal distributions with the means and deviations as you describe, and you get something akin to the answer posted here.
Or to sum it up simply, you add the means of the points ($\mu_{A+B} = \mu_{a}+ \mu_{b}$), and those are your new means, and a variance of $\sigma^{2}_{a+b}=\sigma ^{2}_{a}+\sigma ^{2}_{b}$ .
I assume you know your standard deviation, as without it your confidence intervals are useless.


Difference between "tournament", "competition" and "match"

Question: I was just reading the article about TopCoder. Before this article I thought a tournament and a competition is the same. What is the difference between tournament, competition and match?
Answer: Match is "a formal contest in which two or more persons or teams compete".
Tournament consists of multiple matches between contestants and comes from "contest between groups of knights on horseback. Modern use, in ref. to games of skill, is recorded from 1761."
Competition does not have such a problem with its meaning of "a contest for something" which is from 1610s.
Differences and relationships:
So, match is a different animal (you can not call a match neither a tournament nor competition).
Every tournament is a competition, but not every competition is a tournament.
You can also look at related term: championship.
References are from etymonline entries for match, tournament and competition.
Answer: To elaborate beyond the definitions already provided, a tournament generally refers to a specific format of competition, where competitors engage in a series of matches to determine the winner(s).
There are several types of tournaments (single elimination, double elimination, round robin, etc.), but generally speaking the goal of the tournament is to provide overall winners through a gradual sorting process based upon success within the individual tournament matches.
A competition can be any of the different types of tournaments, or it can be something less structured (such as two teams playing a single match).
Answer: First, a "match" is usually between two parties as contestant, where as a "tournament" or a "competition" is for multiple contestant.
A tournament, is a series of matches. There are generally a large number of contestants
A competition can include a tournament, or a match. It's a more general sense, and includes anything, in which there is one or more parties contesting. A competition can consist of only one contestant, which "tournament" and "matches" can't have. That's the only differences I can think up of.
Comment: How about comparing to championship?
Answer: A tournament is a contest where teams or individuals compete but not necessarily against each other. It usually lasts a short period of time. Competitors are eliminated along the way, until you get to the final of two teams or competitors where the eventual winner is decided.
A competition on the other hand is a contest where all participants competes against one another, usually on a home and away basis. It generally lasts for weeks or months. No one is eliminated and the winner is the one that has accrued the most points.
Comment: Please cite reputable sources or specific expertise to back up your answer.


Strategy for studying professional games?

Question: I recently took A. Dinershtein's Go style test. It was useful to me, as the test is aimed at finding professional players who might think the way you do, for study purposes. It has definitely worked for me. But what should I bear in mind while studying professional games?
Comment: Dumb question, I took the test, but it didn't give me a list of professional players to study.  Where can I find such a list.  I got the "flexible" result.
Answer: A lot depends on your strength.  I find that memorizing them is useful for me.  I've also heard a lot of people suggest that you need to play them out on a real board.  It helps teach your fingers where the pro moves are :)
If you're not a dan-level player, you probably shouldn't focus too much on fighting sequences - you won't be able to understand all of the variations the players are considering.
It's a really good idea to look at each sequence or exchange in the game and try to tell what each player got out of it.  From an amateur perspective almost everything that happens in a pro game is an even trade, so you should look for sequences that don't seem even to you and try to figure out why they actually are.
Comment: "almost everything that happens in a pro game is an even trade." Unless one of the (pro) players (or a third pro) says it's not.
Comment: In which case, it is usually going to be close enough to even for the vast majority of amateurs. As Janice Kim one pointed out in a lecture: if an amateur played as well as the losing player in every pro game, they'd still be much stronger than most amateur players.
Answer: Most pro games are fairly even until a "turning point." This is when one player makes a mistake, as related by the author of the game commentary, usually a pro. Sometimes the commentator is one of the players, who says, "I made move X that lost the game, or "My opponent's move Y lost him the game."
Then the thing to do is to study the game up to the turning point, to see why it was even till then, and then after the turning point, to see why the winner had a clear advantage.
Some games are closely matched to the end, with White finally winning by less than the komi, or alternately, Black beating komi by say, one and a half points.
A model book in this regard is Kato's "Attack and Kill," about his winning streak of some 20-odd games, in which he points out his opponent's "losing moves." He is also self-critical, pointing out places where he made move X, which should have lost, but that the opponent's move Y was an even worse mistake, that resulted in a Kato victory.
Answer: I used to memorize games as a fairly large staple of my studies. Some general points:
1) The position at any point is approximately even.  A "losing move" to a professional–one that everyone agrees is bad–is still probably close enough to even for anyone but a high-level dan.  If you are at that point or getting close to it, be sure to look up the commentaries if there are in and read through them.
2) Take your time on each move.  Analyze how you would move, see how the professional moves, and analyze why the professional might have moved there.  It is oft repeated that you are about 3-4 stones stronger when you study, so take advantage of that and try to see as much as you can. Even if you are wrong, the process of thinking about it is very valuable.
3) Start with ten moves at a time and see if you can increase it over time.  So put down ten moves, then reset.  When I would do it I would go back to a blank board every ten moves and try to play back to the current point.
4) Replay your own games from memory immediately after you play them.  If you played a person at a club, see if you can get them to go with you.  Memorizing pro games is training your pattern memory, and replaying through your own games after you've played them is excellent practice here.
5) During the endgame try to count the value of each move.  This is an easy time to do that, and it is excellent practice.
Hope that helps!
Answer: Replay through a game twice.  Each time focus on just 1 side.  Memorizing games can help, but  it's even better to memorize games that cover variations and/or provide commentary.  Don't try  and understand every single move though, that is just too daunting even with provided in-depth commentary.  Instead, try and gain the overall idea and feel the flow behind their play.
Answer: Yuan Zhou just published a book on this topic. Check out Slate and Shell for sample pages. I am a big fan of Zhou's books and will certainly buy this one. He has a nice way of writing towards kyu level players.
Title: Learning from Pro Games
Author: Zhou, Yuan
Year: 2011
ISBN: 9781932001-57-0
Price: $20.00
http://www.slateandshell.com/SSYZ015.html
Comment: nice. i like yuan zhou too. i may have to check it out. hopefully schaak- en gowinkel het paard will have a copy.
Answer: I am a novice player, so take everything I might say cautiously.  But I have been working through "Invincible - The Games of Shusaku" by John Power and I think it has been helping me, even if there is a lot I don't understand yet.
It is mostly commentaries on games from Honinbo Shusaku, who is arguably one of the greatest Go players.  The one thing to keep in mind is that these games were played before Komi was invented, so generally black can be more defensive and white must be more aggressive then you would likely see in a modern competitive game.  Still, the general tactics should remain the same.
Comment: It's a fantastic book.
Answer: I learned the game's rule when I was 5 or 6 years old. However, I was really hooked after I read a go book in a small bookstore in Xian (西安) when I was eighteen. The book was written by Go Seigen (吳清源-名局細解).
The book explains every single detail in games between Go Seigen and other top Japanese Go players. It was so inspiring. It was like reading a great painting. It was just beautiful.
I'd say I fell in love with go because of the journal to Xian.
More than twenty years later, I have written a program on iPad to read the annotated games of great pro players. The first game to test the program with, is a game of Go Seigen XD
So, I'd say pro games, like great paintings, are art.


What is the binding energy of a neutron star?

Question: Neutrons which constitute a neutron star have a rest mass that is greater when separated from the star because they are bound with a certain potential energy. This potential energy causes the system to have less mass. So my question is how much less? Is it significant? Do we measure it?
Comment: It's a bit confusing to call binding energy as potential energy. It's negative potential energy… a deficit that needs to be added to disassemble the system.
Comment: Because the potential energy causes the system to have _more_ mass. When you lift a brick you do work on it. You add energy to it. You give it potential energy. You increase its mass. When you drop it, this potential energy is converted into kinetic energy which gets dissipated, then you've got a [mass deficit](https://en.wikipedia.org/wiki/Binding_energy#Mass-energy_relation).
Answer: This paper is interesting. It uses the method of calculating the number of nucleons in the neutron star, $N$, based on the radius, $r$, the number density as a function of radius, $n(r)$, and the metric function $\lambda$, which comes from the equations of general relativity:
$$N=\int_0^R 4\pi r^2e^{\lambda/2}n(r)dr=\int_o^R4\pi r^2 n(r)\left[1-\frac{2m(r)}{r}\right]^{\frac{1}{2}}dr$$
The binding energy, $BE$, is then
$$BE=Nm_b-M$$
where $m_b$ is the mass of a nucleon and $M \equiv m(R)$.
Answer: The gravitational mass of a neutron star is quite a lot less than its baryonic rest mass (plus the mass associated with the kinetic energy of its contents), because a bound neutron star, by definition, must have a total energy (the sum of its internal energy and gravitational potential energy) that is less than zero.
In a "normal star" this is also true, bit the difference is that the gravitational potential energy of a neutron star can be comparable with its rest mass energy.
How significant is this? It depends on the baryonic mass of the neutron star and the equation of state of the dense matter. For a typical neutron star of 1.4 solar masses and 10km radius, the order of magnitude estimate for binding energy as a multiple of rest mass energy, $GM/Rc^2$, is about 0.2, suggesting a significant reduction in the gravitational mass compared with the baryonic mass.
Comment: Rob, is there a typo above? It reads as if the total energy of the neutron star is less than zero.
Comment: @JohnDuffield Precisely so, as I have defined the total energy. The sum of the internal (kinetic) energy and gravitional PE is less than zero for a bound star.
Answer:
What is the binding energy of a neutron star?

What Rob said is about right. It's about a fifth of the original mass-energy. See Wikipedia:  "Its mass fraction gravitational binding energy would then be 0.187".

Neutrons which constitute a neutron star have a rest mass that is greater when separated from the star because they are bound with a certain potential energy.

Yes. When you lift a neutron all the way out of a neutron star, you increase its mass. It's a bit like lifting a brick. You do work on it. You add energy to it. You give it potential energy. You increase its mass. When you drop it, some of the internal E=mc² kinetic energy is converted into external kinetic energy. This typically gets radiated away, and then you're left with a mass deficit. Of course, to be absolutely precise you consider the Earth too, but it's so much bigger than the brick that whilst momentum is equal and opposite, kinetic energy is not. It's so slight for the Earth that we disregard it.

This potential energy causes the system to have less mass.

Like Blackbody Blacklight said in the comment, potential energy causes the system to have more mass, not less. See what I said above about the brick. Then imagine you start with a zillion neutrons in space. You drop them and they all fall together. As this occurs some of their internal E=mc² kinetic energy is converted into external kinetic energy. This typically gets radiated away, and then you're left with a mass deficit. The neutron star mass is about 20% less than the mass of the original neutrons. That's significant.
Note though that things can get a bit confusing because the zero level for gravitational potential energy is set at infinity. See hyperphysics. So we say that the gravitational potential energy of the neutrons in the neutron star is negative. In similar vein we say the binding energy is negative. Note though that there isn't anything in there that's actually made of negative energy. All you've got in there is neutrons, and they're made of positive energy. There's just less of it, that's all. The mass of each and every neutron has decreased. You hear of things like invariant mass, but when it comes to general relativity, mass varies. See Wikipedia. In fact, it isn't limited to general relativity. The mass of a hydrogen atom is less than the mass of an electron plus the mass of a proton. And because the electron is less massive than the proton, most of the mass deficit can be attributed to the electron. It plays the part of the brick.


What type of 6ft fence should I get, that can take a lot of high winds?

Question: We need to replace our chain link fence with a 6ft fence because 2 of our dogs can jump over it.  We just don't know what type of fence can take a beating from the high winds we get due to the fact that our yard faces the west and there is a huge retention ditch behind us that they us as a field for sports when its not filled with water, so when it is a windy day, a bad thunderstorm, or a snow/ice storm we want our fence to be able to last a while.  We have lived in our house for 12 years and have seen my neighbor replace their wood fence 3 times and I notice that the wood starts to splinter fast. My other neighbor has the PVC fence for about 5 years and had to replace a couple of sections twice.  Also we have had to replace our storm screen door on the back door 3 times since we have lived here due to the winds blowing them off. Looking forward to hearing what you recommend.
Comment: related questions http://diy.stackexchange.com/questions/51864/what-is-the-best-type-of-6-ft-wood-fence-to-block-wind-in-a-yard and http://diy.stackexchange.com/questions/27705/how-much-will-a-board-on-board-shadow-board-fence-reduce-the-wind-load?lq=1
Answer: How much is "a lot of high winds"? I have a classic cedar panel fence (now with pressure-treated posts; it was time to redo them all and PT lasts in ground contact better than cedar), and it has withstood a couple of microbursts and the like with little or no damage. It did lose one board from one panel and a couple of post caps and cap strips over the years (which I also had cleaned up as part of this redo), but not much more than that.
Use good materials (PT in ground, PT or a weather/insect-resistant wood like cedar above ground), set the posts properly, and a wood fence can be good for 20 years with only minor maintenance.
Comment: On the other hand, don't bet too much on the dogs not tunneling under or finding some intermediate surface to jump on. Some are quite accomplished escape artists. But I'm not the right person to advise on what's most likely to work longest; I can speak dog but I think cat.
Answer: Chain link is probably what you want to stay with. It will survive hurricane-force winds (little resistance), is low-maintenance, dog-proof and provides excellent security. If the hounds can jump 6 feet you can easily get 8 foot chain link.
But (and it's a big one) you don't install chain link fence on the cheap. Poles must be anchored in concrete, corners must be braced against the next pole and it must be tensioned properly.
If the dogs like to dig, rent a small ditch digger like the kind used for sprinkler systems. You can then simply bury the fence 2 feet down.
Comment: I have had a few dogs that were real diggers. I found burying a layer or 2 of chicken wire 4-6" down 1 foot wide on the inside of the fence stopped them when they hit the wire.
They always started within a few inches of the fence so I doubled that. It was a recommendation from a friend not my idea but both of my big escape artist quit digging at the fence after several times hitting the wire.
Comment: I know this is an old question, but if you need an eight foot fence and bury two feet of it to hinder tunneling you have a six foot fence that you originally had.
Answer: Any wooden type with 4x4 or 5x5 post sat in a 2foot hole using concrete. But leave a small gap between the pickets for the wind to blow though.


Differences between hashed text and encrypted text

Question: I was wondering if it's possible to tell if the text is hashed or encrypted. For example, if someone has given you a a chain of random characters. Would you be able to tell if it's encrypted? Which you could be able to retrieve the original text by having the private key. Or it's hashed which there is no way to reverse it.
Comment: Does this answer your question? [Differences between hash- and encryption algorithms?](https://crypto.stackexchange.com/questions/62036/differences-between-hash-and-encryption-algorithms)
Comment: @kelalaka Nope, I have read this. I know the differences of hash and encryption. Just wondering about the end result.
Answer: Hash is very short, e.g. 8 bytes, 32 bytes, 64 bytes, no matter how long the original text is. Where as encrypted text is actually unlimited.
If the encrypted text is relatively long, you can calculate some statistical values. Where as hash is short and is no sufficient for any statistics. E.g. how will you speak about some frequency if you only have 32 bytes?
Hash is a one way transformation. In a normal case there is no way to restore the original text. If you had a text of 1000000 bytes and hash of 64 bytes, it is clear that  there is no way to obtain 1000000 bytes from 64 bytes.
To randomness: It is one of the goals of good encryption to make the encrypted message indistinguishable from a random sequence of bytes.
Answer: mentallurg already spoke about the possible length differences. I want to note that if you can intercept several texts you maybe be able to look at some distribution properties. Encrypted texts will frequently be from a particular subspace, say a group and while they may be randomly distributed in that subspace, they may not look randomly distributed in $\{0,1\}^k$ whereas hashed text is likely to look randomly distributed in the space $\{0,1\}^k$.
I also want to note that none of this is necessary theoretically because you can easily make examples of pairs of encryption schemes and hash schemes whose outputs are identically distributed. If you have more specific details about either function, it would probably go a long way in helping you distinguish between them.
Comment: A good block cipher is expected to be a PRP. Why they will not look randomly distributed?
Answer: If given only the a sequence of bits, I do not think you can distinguish between the two, that's the reason both these mechanisms can be effectively used as PRNGs if implemented correctly.
You would need some more information about this sequence generating blackbox in order to figure out what you are dealing with. For example, let's say you are able to feed it input, and then observe the output to establish correlations between them. If it always gives you a 160 bit output and is also deterministic (i.e., same input results in same output), then, you guessed it right - you have a SHA1 hash. If it's an encryption, then longer the input message longer would be the output (deterministic or not would depend on the encryption method used). In any case, you would need to gather more information such as this before you can say whether it's a hash or an encryption.


LEGO for a 1 year old

Question: I have a son who has just turned one. I like my LEGO and my desk at work is covered in minifig's etc, the problem is my wife isn't as keen on them. I was wondering can anyone recommend a set that would be appropriate for me to get for my son so I can bring my hobby home without feeling the wrath of my wife, or is it a bit too soon to introduce him to LEGO?
Comment: Be honest. You're buying these for yourself? or your son? :) If for yourself, don't bother. Duplo is incredibly frustrating to play with if you're used to Lego. If for your son, I suspect at 1 he won't be that into it, but eventually he'll figure it out. But there's no hurry, and it won't scratch your lego itch.
Answer: LEGO bricks aren't suitable for children under 3 as they are considered a potential choking hazard.
LEGO also sell a DUPLO brand of construction toys which are twice the size of regular bricks. DUPLO bricks are designed for children aged 1½ to 5 years old.
Comment: Note that some of the DUPLO sets include shovels, flags, and other small items which could be dangerous.  So stash those bits away for a couple years...
Answer: LEGO Group also did a range called LEGO Baby or Primo, which was pretty much suitable from birth.
It's not currently in production, but does come up on ebay and the like now and again, and is slightly inter-usable with Duplo and hence standard LEGO blocks.
Items ranged from things like this rattle, with chewable petals:

To the more "advanced" building sets:

My sons both enjoyed their Stacking Jungle Set, and the Bathtime Boat is still going strong ;)
Comment: Lol, this pic is epic :D [Flower Teething Rattle](http://i.stack.imgur.com/gBHA5.jpg)
Answer: There is also a non-Lego product from Megabloks that is really good for young children.  They studs on those blocks are rounded so they're easier to kids to get them to "lock" together.  While not as sturdy as some of the Lego products, they do seem appropriate for real young children.
Comment: Seconding this, they are actually QUATRO-scaled and would sorta link up to the DUPLO/regular sized stuff but only on the bottom. Either way I got 2 large boxes of them and all 3 kids love them also because the builds get HUGE very quickly.
Answer: In addition to DUPLO, there is also QUATRO. They are, as expected, 4X the size and impressively compatible with standard sized and DUPLO. I inherited some, so have no idea if they are still made or sold.

LEGO for a 1 year old


How to be sure that you are not tracked with anti-theft software or similar when using tab previously owned by someone?

Question: I have seen the amount of pictures and personal data an anti-theft software can dig on person using a stolen phone. How can one make sure that he is not tracked through similar software when using a previously owned tab/phone? I understand that a factory reset is not enough in most cases.
Comment: Nothing personal, as far as I know, but I hope this is very difficult -- I had a tablet stolen a few months ago, and it stayed "not located" on Google Device Manager for a couple months, then just dropped off.
Comment: In all honesty, if you buy used, you get used. In any object, be it computers, cars, furniture, tickets, etc. you always have a measure of "Buyer Beware" going on. As for your tablet, flash a fresh ROM on it. Anything short of that - no guarantees, maybe not even then.
Comment: My folks bought the tab. I was thinking of flashing a new ROM on it. Just wanted to make sure what is enough. I think the tape stays on the cameras even after the flash...
Answer:
I understand that a factory reset is not enough in most cases.

A factory reset is usually enough if performed through Settings, which removes Factory Reset Protection from the device (a reset from Recovery does not do this).  This will also unlink Android Device Manager and remove most other tracking tools.
If you are concerned about apps that may have been integrated into the system image, then yes you should flash a custom recovery and then a ROM (selecting the wipe option).  Unless there is a malicious bootloader installed (unlikely) then this will more than suffice.  You might also want do delete anything from <code>/sdcard</code> and format any external SD cards just to ensure that no malicious files are left there that you might accidentally use.
Comment: I did as you suggested and feel more secure already. The custom recovery provided an option to format the whole device. Thanks!


Can't seem to connect with PuTTY

Question: generated the required .ppk file and loaded it in Connection=>SSH=>Auth=>Private key file for authentication.
The connection ERROR message: Network Error: Connection refused.
Am i doing something wrong ?
Answer: The error message means that PuTTY can't even get as far as connecting to the ssh server and presenting the key.  Things worth checking are if you can ping the host you're trying to connect to, and it's behind a router that the required port (usually 22) is forwarded, and that the ssh server is actually running.  Or it could be you've been locked out due to too many failed attempts as Ryan said, in which case try from a different computer.
Are you on the same network as the server or are there routers in between?
Answer: Sounds like the SSH server is explicitly not allowing connections from you. Perhaps you tried too many times and got locked out?

Can't seem to connect with PuTTY


Copying a selection without adding a new layer in Krita

Question: I want to duplicate a selection area in Krita and move it to anywhere I wish. The problem is, I can't do this simple manipulation because it creates an additional layer each time copied and pasted, which is not something I expect for ultra simple drawings such as black-and-white stickman sprite sheet. I have already used clone brush but it is not practical.
Comment: You could always use mac or windows + photoshop ;) --- For anyone thinking about answering **TL;DR summary of the comments:  _No solution yet._**
Comment: I don't know too much about Krita, so I can't really say if it has the functionality you're looking for, but in photoshop you can do that with the `Move tool` by first holding down `Alt` and then dragging the selection. Maybe that exists in Krita as well.
Comment: I have tried what you said but it dragged the selection frame with everything else except my desktop :) I was even more comfortable with my own amatour drawing program I wrote with C++ and OpenGL because it was one of the rare image editting programs I used to extensively know about :P
Thanks anyway for trying to help, for paying attention to my question.
Comment: Maybe try gimp? [I'm pretty sure it handles pasting very close to how you want it](http://docs.gimp.org/en/gimp-selection-float.html). Krita is more of a drawing/painting application anyways.
Comment: That was why I prefered krita to gimp. I want to be able to draw things from scratch rather than photo-editing. It makes drawing simple shapes such as rectangle,circle efficiently almost impossible. Like a torture. Thanks for advice. I'll probably also look for other alternatives for drawing/painting on linux.
Comment: I still have one advice left in me, given that you are not so interested in Gimp. Not sure if you feel this makes it any better, but I do know enough to say that merging layers works the same way in Krita as it does in Photoshop. `Ctrl+E` merges selected layers or currently selected layer with the one below it. So what you could do is: `Ctrl+C, Ctrl+V, Move, Ctrl+E`. Not as simple as just `Alt+dragging`, but should do the job. It's one extra hotkey compared to what you were asking about.
Comment: I was already aware both that I could merge layers and that this would be too cumbersome. Again, very thanks for all your attempts to help.
Answer: This cannot be done, and quite frankly there is no need for such a feature (pasting on new layer is already a special feature). While you're at it please ignore these "use photoshop" scrubs who think everyone can throw mountains of cash at software they don't even know how to use (or much less even need when there are free alternatives like Krita and GIMP...)
What you can do instead is use the "Merge with layer below" option.
Paste an item onto a new layer (ctrl+v) work it as you will, and then merge it down to the layer below (ctrl+e) problem solved. You can also simply forget the layers are even there (they don't make a difference after you save the file into a format that doesn't support layers like PNG or JPG)
If you do not like this, bring it up for discussion in kritas development forums (see also here) as a feature request.
Comment: When you merge two layers, the merge happens on ALL frames of a timeline. That means you must visit all the frames and delete everything from that pasted layer for each frame except the one you want to merge to. That is highly inconvenient and not really a solution. I will rather use traditional pen and paper at that point.
Comment: pasting into a new layer then merging down is not the same thing as pasting into the current layer if your selection includes any non-opaque pixels.
Comment: No, it's not the same result. The translucent areas will be darker with the layer merging than if the pixels had been replaced in the original layer.
Comment: @Sparr yeah it is... Same result anyhow. Also even if you were right, this does not make my answer bad (I did answer that there is no solution; and I did mention the one and only way to have this issue fixed; by bringing it up with the development team).
Comment: @Sparr this depends entirely on the program and implementation of these features, and since Krita does not have the feature you speak of you cannot deny the possibility that if implemented it would be the same. It may behave as you say in some program that you use, but logically speaking the translucent areas should always get less translucent when you copy and paste it over itself, that is pretty basic...
Comment: the original question said "duplicate" and "move", with no mention of color/transparency mixing. If I duplicate a RGBA(200,100,50,127) pixel and move it somewhere else, I want the target pixel to end up RGBA(200,100,50,127), not a 50/50 mix of RGB(200,100,50) and whatever was in that location before the operation.
Comment: "no need for such a feature" - To be honest, if you're into pixel art or simple sprite animations, this feature could be DAMN handy.
Answer: This is a terrible workaround, but I have found that when I want to perform this operation I will paste into a new layer, then select the pasted area, then select the original layer, then delete the pasted area, then merge the new layer down to fill the hole.
Answer: You can't paste into existing layer in Krita. Sparr's workaround doesn't work in animation.
But there is one other workaround. The idea is to keep that layer visible only for a set of desired frames. After adding the pasted content, copy it into the desired frame using the "Copy frame" context menu option. Then go to the first frame of the animation and remove that pasted layer from the first frame using "remove frame" context menu option. That way, the pasted content will only appear when you want it to. Then once you are done with the pasted content, you can go to the frame where it needs to disappear and choose the "new frame" context menu option.
It isn't very intuitive, and once you remove all existing frames of a layer, the layer will lose its contents.


fastest way to backup webserver files and mysql db and automate

Question: I would like to setup a cron job for to backup all my web server files to a compressed file and also my MYSQL db. I have full acces to my server as it is a VPS. I am a noob at linux and could really use the help. I am also running centos 5. I would appreciate any help I can get. Also what is the fatsest method to do this.
Answer: Depending on the size of your site one if the easiest ways would be to do a database dump, create a tar.gz archive of your site directory and dump file and email it to an external location.
Look for example scripts on using tar and MySQL database dumps. The hardest part for new admins in this kind of setup is getting the email working. If you don't already have an email server set up it is probably easiest to use gmail or equivalent.
I have a couple clients that use almost this exact method. If you want more detail just ask.
Answer: I used to do exactly what Tim Brigham described but these days I no longer compress the dump files. Instead I use rsync to transfer the files. Because most databases only change relatively little between backups and rsync only transfers the changes the data is transferred much faster. This can be of particular benefit with largish dump files.
Comment: True.. I didn't want to get into differential backups or the need to run a second system for pushing or pulling the backups.
Answer: I agree with John Gardeniers, rsync is great. Not too difficult to configure, can be automated and very powerful. You may also check with your host to see if they offer a backup solution. Some of the more reputable providers offer full server backups at VERY reasonable rates.