filling regions of matrix

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Hi have a matrix.
I =
0 0 0 1
0 0 1 0
0 1 0 0
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1
Here ones in the matrix has divided the matrix in 3 regions.Is it possible to have the following type of output:
I =
2 2 2 1
2 2 1 1
2 1 1 1
1 1 1 1
3 1 1 1
3 3 1 1
3 3 3 1
Thanks

Accepted Answer

Andrei Bobrov
Andrei Bobrov on 26 Jun 2011
Iout = bwlabel(~cumsum(I,2))+1

More Answers (1)

the cyclist
the cyclist on 26 Jun 2011
There might be more efficient ways, but this will get the job done. I hope I didn't just do your homework for you.
I = [0 0 0 1; ...
0 0 1 0; ...
0 1 0 0; ...
1 0 0 0; ...
0 1 0 0; ...
0 0 1 0; ...
0 0 0 1];
[M,N] = size(I);
J = I;
for nj = 1:N
% Find the ones in this column. Algorithm OK even if there's only one of them.
firstOne = find(I(:,nj),1,'first');
lastOne = find(I(:,nj),1,'last');
J(1:firstOne-1, nj) = 2;
J(firstOne:lastOne,nj) = 1;
J(lastOne+1:end, nj) = 3;
end
J

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