islocalmax dont find the first maximum

Hello,

if i use islocalmax for a signal like A=[12;12;4;65;43;34;6;7;7;3;768;324;564;23] Matlab throws

ans =

14×1 logical array

0 0 0 1 0 0 0 1 0 0 1 0 1 0

Why Matlab cant find one of the first maximum [12]?

Thank you for help.

Answer 1

[Guillaume]

Why Matlab cant find one of the first maximum

Because matlab wants it to be truly a local maxima, that is it needs to be preceded (or followed at the right edge) by lower values. If it's critical that matlab identifies the first (or last) element as a local maxima if the initial (final) slope is downward (resp. upward) then surround your array by -Inf:

A=[12;12;4;65;43;34;6;7;7;3;768;324;564;23];
ismax = islocalmax([-Inf; A; -Inf]);
ismax = ismax(2:end);  %to remove the -Inf from the result

[Silvio Risse]

Thank you for your help!