MATLAB: Compress down a 1000×1000 matrix into a 100×100 matrix

MATLABmatrices

I have a 1000×1000 matrix that contains various values. I would like to compress it down into a 100 by 100 matrix by averaging each 10 by 10 cell's values into 1, but im not really sure how to go about doing this

Best Answer

If you have image processing toolbox
M = rand(1000, 1000);
M_new = blockproc(M, [10 10], @(x) mean(x.data, 'all'))
Alternative Solution 1: (surprisingly the fastest)
M_new = conv2(M, ones(10)/100, 'valid');
M_new = M_new(1:10:end, 1:10:end);
Alternative Solution 2:
M_C = mat2cell(M, 10*ones(1,100), 10*ones(1,100));
M_new = cellfun(@(x) mean(x, 'all'), M_C);
Alternative Solution 3:
M_new = zeros(size(M)/10);
for i=1:100
    for j=1:100
        M_new(i, j) = mean(M(10*(i-1)+1:10*i,10*(j-1)+1:10*j), 'all');
    end
end
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