MATLAB: How to find nearby labels

labelsregion

I have matrix I and I want to show that region with label 1 is neighbours with regions with label 2 and 4. Or region with label 2 is neighbour with region 1,4,5,and 3.
I =
1 1 1 2 3 3
1 1 2 2 3 3
4 4 4 5 5 3
4 4 4 4 5 5

Best Answer

I =[...
     1     1     1     2     3     3
     1     1     2     2     3     3
     4     4     4     5     5     3
     4     4     4     4     5     5];
 
N = unique(I);
n = numel(N);
out = cell(n,2);
for ii = 1:n
    out(ii,:) = {ii, unique(I(bwdist(I == ii,'chessboard')==1))};
end
or
N = unique(I);
n = numel(N);
out = cell(n,2);
o3 = ones(3);
for ii = 1:n
    lo = I == ii;
    out(ii,:) = {ii, unique(I(imdilate(lo,o3) + lo == 1))};
end
out_as_table = cell2table(out,'v',{'number','neighbours'})
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