Find maximum of each cell array element efficiently

Question

We have foe example a 3x5 cell array where each element is a matrix. Can we find the maximum of each cell element, i.e, a matrix, and store the corresponding value in a new 3x5 matrix? All this without for loops. Bellow there is the naive way.

Example:

a = rand(5,6);
b = rand(7,6);
c = rand(7,9);
d = rand(27,19);
CellArray = cell(2,2);
CellArray{1}=a;
CellArray{2}=b;
CellArray{3}=d;
CellArray{4}=c;

MaxResults = nan(size(CellArray));
for i=1:numel(size(CellArray))
    MaxResults(i) = max(max(CellArray{i})); 
end

Thank you.

Note that in your code you could replace max(max(CellArray{i})) by max(CellArray{i}(:)) (as in @Jonas's answer), which is probably faster — Luis Mendo
– Luis Mendo, Commented Jan 30, 2014 at 11:28
Also I highly doubt you want your loop to go to numel(size(CellArray)) but rather to just numel(CellArray) — Dan
– Dan, Commented Jan 30, 2014 at 11:37
@LuisMendo: max(max(CellArray{i})) is actually faster than max(CellArray{i}(:)) for large inputs. — Daniel
– Daniel, Commented Jan 30, 2014 at 11:48

Jonas · Accepted Answer · 2014-01-30 11:24:20Z

7

Not guaranteed to be that much more efficient (until Matlab decides to multithread it), but you can use cellfun like this:

MaxResults = cellfun(@(x)max(x(:)), CellArray)

answered Jan 30, 2014 at 11:24

Jonas

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