Question

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.

Answer 1

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);