Stop for-loop at the second last column

E.g. I have a vector a = [1 1 5 1 1 1 10 2]; Error appeared when the loop reached the last column. I am writing to stop at end-1, but kinda lost. Please help solve this. thanks in advance.

function z = findpeaks(a)
 for i = 2:[a(:,end-1)]
 z  = a(a(i)>a(i-1) & a(i)>a(i+1))
 end

[Dennis]

I think your loop has a creative synthax (not wrong though).

What bothers me is that your loop runs from 2 to the 2nd last value in a, so the amount of iterations depend on your vector entry:

a = [1 1 5 1 1 1 10 2]; %10 iterations
a = [1 1 5 1 1 1 1 2]; %1 iteration
a = [1 1 5 1 1 1 -10 2]; %does nothing
a = [1 1 5 1 1 1 0.5 2]; %does nothing

I am not sure if this is intentional.

Also i recommened to rename your function since findpeaks() is already implemented in matlab.

Maybe you should check the Matlab version out, i guess you want to try something similar:

[peakval,peakloc]=findpeaks(a)

peakval =

     5    10


peakloc =

     3     7

[HYZ]

Sorry I didn't explain my problem well. Basically I would like to get values which are larger than the value before and after. That's why I tried to put something like i=2:end-1. The loop has problem when it reached '2' as it has no vlaue after it.

Answer 1

[Adam Danz]

Here's how to start at the 2nd column and stop at the second to last column

 for i = 2 : size(a,2)-1   %or     for i = 2 : length(a)-1     if a is a vector
    ...
 end

Also, matlab already has a function named findpeaks() so you might want to rename your function.