MATLAB: Row numbers of the first zero, repeated

Question

I have a column vector of 7000 data points… of the pattern 0 0 0 0 30 60 90 120 119 118…. 2 1 0 0 0

I want to return the row number for the last cell before the number turns into a 0, every time this happens

Note: All the numbers are variable, and the sequences I want to extract varies in length.

To pick out the maximums I used [pks locs]=findpeaks(a(:,1)), want to do similar for just before the zeroes appear…

Answer 1

Your first element is a zero. Should that be included in the output? So you just want the last non-zero number in a stretch of non-zero numbers before it turns into a 0, right? Try this:

m = [0 0 0 0 30 60 90 120 119 118 2 1 0 0 0 3 4 0] % Create sample data.
dm = diff(m~=0) % Threshold and find element-to-element differences.
lastElements = find(dm == -1)  % Find the indexes where it goes to zero.