Matlab's Find Function

Throughout my entire undergraduate studies at UNH there was a great deal of interaction with MATLAB; however, I was never exposed to one of the nicest functions in MATLAB until grad school. The function I am referring to is:

find

Find, is a very powerful function that can be used to help you search for certain elements in an array. Lets start off with a practical application of "find". Suppose you have a voltage signal that is stored in two arrays. The first array contains all the sampled voltages (lets call this array vArray) and the second array contains the timing information (lets call this array tArray). Suppose we want to determine where all the zero-crossings are in the signal and then pull the corresponding timing information from it. Just follow this code:


And Here is a plot of the Results


As you can see, I detected every zero crossing point in the signal. Now if this was a real system, I probably wouldn't want to detect the zero crossings with the noise that I have; in which case I would want to apply a low-pass filter of some sort that restricts the detection to the intended signal, but that is out of the scope of this topic.

Now it's your turn to play around with "find".