How can I find the maximum or minimum of a multi-dimensional matrix in MATLAB? [duplicate]
I have a 4D array of measurements in MATLAB. Each dimension represents a different parameter for the measurement. I want to find the maximum and minimum value and the index (i.e. which parameter) of each.
What's the best way to do it? I figure I can take the max of the max of the max in each dimension, but that seems like a kludge.
Quick example:
%# random 4 d array with different size in each dim
A = rand([3,3,3,5]);
%# finds the max of A and its position, when A is viewed as a 1D array
[max_val, position] = max(A(:));
%#transform the index in the 1D view to 4 indices, given the size of A
[i,j,k,l] = ind2sub(size(A),position);
Finding the minimum is left as an exercise :).
Following a comment:
If you do not know the number of dimensions of your array A and cannot therefore write the "[i,j,k,l] =
" part, use this trick:
indices = cell(1,length(size(A)));
[indices{:}] = ind2sub(size(A),position);
for two dimensional array, say I
you can just use the min /max function twice.
n times for n dimensional array.
eg: a=[2 3 4; 5 6 7; -2 7 87; 911 7 34];
for minimum: min(min(a,[],1))
-> the answer will be -2.
you can put the dimension parameter in min/max to 2 as well. as this is calling the function twice, second time on the minimum/maximum element vector of the dimension u choose.
similarly, you can do (max(max(a,[],1))
to find out the maximum.
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