How to detect if a signal raises sharply or slowly? so how can i detect if a signal raises sharply or not ? Are there easy solutions (i suppose there are) ?

the problem is that if a signal raises sharply, i need less data to not pollute the dataset and if the signal raises slowly then i need more data. But how to determine the number of data, without knowing if it's sharp or not?

Also I need to know if it raises sharply when i'm at the top of the curve, NOT afterwards (in realtime if you want)

thanks so much

here is two examples of signals
http://khaelis.com/downloads/screenshotSharp.jpg
http://khaelis.com/downloads/screenshotSlow.jpg

Jeff
I believe that you can calculate the derivate which is the rate of signal change. In discrete signals this is obtained (approximated) by:

$$x'[k] = x[k]-x[k-1]$$

(by other words, it's the difference between consecutive samples)