MATLAB: How to efficiently find maximum of selected indices of an array in MATLAB

MATLABvectorization

Let us say we have the vectors: w, s_on, and s_off. s_on and s_off have the ascending indices of the onset and offset of an event. We need to find the maximum value in during each event. How can we do it without using loop. for example we may have the following values:
    s_on = [5 19 78 101];
    s_off = [10 28 97 152];
    w = rand(1,200);
The following code does not work:
    pv = max(w(s_on(1:end):s_off(1:end)))

Best Answer

You don't have a choice, a loop is required for that. Either an explicit one:
pv = zeros(size(s_on)); 
for idx = 1:numel(s_on)
  pv(idx) = max(w(s_on(idx):s_off(idx)));
end
Or through an arrayfun:
pv = arrayfun(@(s, e) max(w(s:e)), s_on, s_off);
It is likely that the explicit loop will be faster.
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