MATLAB: How to fill gaps in a matrix with a numbers using interpolation to develop a contour.

MATLABmatrix manipulation

M =
     0     0     0
     0     0     3
     0     3     0
     3     0     3
     0     3     0
     0     0     3
     3     0     0
     0     0     0
in this M matrix, using interpolation i want to fill gaps with 3s between any 3s. for example, in first column, first 3 is in the 4th row and last 3 is in the 7th row. i want to fill rows 5 and 6 also with 3s. same for other columns.
Thanks and regards for all cooperation

Best Answer

M(cumsum(M) & cumsum(M,1,'reverse')) = 3;
or for:
M =[0 0 0; 2 2 3; 3 3 0; 0 0 0; 3 3 0; 2 2 3; 0 0 0; 3 3 2; 0 0 0; 3 3 3];
s = join(string(M)','');
[a,b] = regexp(s,'30+3');
lo = false(size(M));
for ii = 1:numel(a)
    for jj = 1:numel(a{ii})
        lo(a{ii}(jj)+1:b{ii}(jj)-1,ii) = true;
    end
end
M(lo) = 3;
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