Question

I’ve have been using findpeaks in MatLab to locate the maximum and minimum points of a waveform with no problem, but in the last 20 minutes or so the error:

??? Subscript indices must either be real positive integers or logicals.

Has appeared an I have no idea why. Even trying simple exercises with test data has resulted in the same error. For example if I were to have the dataset:

test = [ 0.1 0.5 0.9 0.5 0.2 0.6 1.0 0.7 0.3 0.1 ]

and used the code:

peaks = test(findpeaks(test));

I would expect the result:

peaks = [0.1 0.9 0.2 1.0 0.1 ]

but for some reason this is no longer the case.

Please advise.

Answer 1

Findpeaks returns the peak values, not their indices. Try this.

peaks=findpeaks(test)

If you want to find the local minima as well,

peaks = [findpeaks(test) -findpeaks(-test)]