title: R: Find missing timestamps in csv
body: <p>as I failed to solve my problem with PHP/MySQL or Excel due to the data size, I'm trying to do my very first steps with R now and struggle a bit. The problem is this: I have a second-by-second CSV-file with half a year of data, that looks like this:</p>
  
  <pre><code>metering,timestamp
  123,2016-01-01 00:00:00
  345,2016-01-01 00:00:01
  243,2016-01-01 00:00:02
  101,2016-01-01 00:00:04
  134,2016-01-01 00:00:06
  </code></pre>
  
  <p>As you see, there are some seconds missing every once in a while (don't ask me, why the values are written before the timestamp, but that's how I received the data…). Now I try to calculate the amount of values (= seconds) that are missing.</p>
  
  <p>So my idea was</p>
  
  <ol>
  <li>to create a vector that is correct (includes all sec-by-sec timestamps), </li>
  <li>match the given CSV file with that new vector, and</li>
  <li>sum up all the timestamps with no value.</li>
  </ol>
  
  <p>I managed to make step 1 happen with the following code:</p>
  
  <pre><code>RegularTimeSeries &lt;- seq(as.POSIXct("2016-01-01 00:00:00", tz = "UTC"), as.POSIXct("2016-01-01 00:00:30", tz = "UTC"), by = "1 sec")  
  write.csv(RegularTimeSeries, file = "RegularTimeSeries.csv")
  </code></pre>
  
  <p>To have an idea what I did I also exported the vector to a CSV that looks like this:</p>
  
  <pre><code>"1",2016-01-01 00:00:00
  "2",2016-01-01 00:00:01
  "3",2016-01-01 00:00:02
  "4",2016-01-01 00:00:03
  "5",2016-01-01 00:00:04
  "6",2016-01-01 00:00:05
  "7",2016-01-01 00:00:06
  </code></pre>
  
  <p>Unfortunately I have no idea how to go on with step 2 and 3. I found some very similar examples (<a href="http://www.r-bloggers.com/fix-missing-dates-with-r/" rel="nofollow noreferrer">http://www.r-bloggers.com/fix-missing-dates-with-r/</a>, <a href="https://stackoverflow.com/questions/16787038/r-insert-rows-for-missing-dates-times">R: Insert rows for missing dates/times</a>), but as a total R noob I struggled to translate these examples to my given sec-by-sec data. </p>
  
  <p>Some hints for the greenhorn would be very very helpful – thank you very much in advance :)</p>