Create an array from a loop in MATLAB?

Question

Here is my Matlab code:

Length = length(High);
i = 1;
j = 20;

while i < Length
     HighestHIGH(i) = max(High(i:j));
     i = i+1;
     j = j+1;
end

This gives an error at HighestHIGH line. What i am trying to accomplish is: Lets assume High is an array of length 100 (Length = 100). I want to get the highest numbers of in sets of 20 in new array. Ex:

HighestHIGH[1] = max(High(1:20));
HighestHIGH[2] = max(High(2:21));
HighestHIGH[3] = max(High(3:22));
...
HighestHIGH[80] = max(High(81:100));

"An" error is never enough. What kind of error? "Index exceeds matrix dimensions"? When i==Length-1, then j==Length+18` which exceeds the size of High. — Andras Deak -- Слава Україні
– Andras Deak -- Слава Україні, Commented Sep 27, 2015 at 0:27
You could use filter to achieve the same in a single line of code — Daniel
– Daniel, Commented Sep 27, 2015 at 0:32
@Daniel, how about adding that as an answer? It should definitely be done with that (even though the original question is "why doesn't this work?". — Andras Deak -- Слава Україні
– Andras Deak -- Слава Україні, Commented Sep 27, 2015 at 0:42

Andras Deak -- Слава Україні · Accepted Answer · 2015-09-27 00:30:26Z

1

When i==Length-1, then j==Length+18 which exceeds the size of High. The upper limit of your loop is too high.

I'd write this:

N=20;
HighestHIGH=zeros(length(High)-N+1);
for i=1:length(High)-N+1
   HighestHIGH(i) = max(High(i:i+N-1));
end

Note that with what you want, the final term is HighestHIGH(81)=max(High(81:100)).

answered Sep 27, 2015 at 0:30

Andras Deak -- Слава Україні

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