finding region

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Mohammad Golam Kibria
Mohammad Golam Kibria on 29 Jun 2011
Hi I have a matrix as follows:
I=
1 1 0 0 0 0 0 0 0 0
0 0 1 1 0 0 0 0 0 0
0 0 0 0 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
Here 1 has divided the matrix in two parts I need to have the indices of these two separate parts. say idx1 will be upper zeros and idx2 contains lower zero indices.Can any one help.

Accepted Answer

Andrei Bobrov
Andrei Bobrov on 29 Jun 2011
BW2 = bwmorph(I,'diag');
L = bwlabel(~BW2);
Id1 = bwdist(I,'chessboard') == 1;
for i1 = 1:max(L(:))
L(bwdist(L == i1,'chessboard')==1 & Id1) = i1;
end
idx1 = find(max(L(1,:))==L);
idx2 = find(max(L(end,:))==L);
EDIT as at Sean
L = bwlabel(~I,4);
idx1 = find(max(L(1,:))==L);
idx2 = find(max(L(end,:))==L);

More Answers (2)

Sean de Wolski
Sean de Wolski on 29 Jun 2011
CC = bwconncomp(~I,4);
CC.PixelIdxList will contain the linear indices. To get the sub indices either use regionprops with the 'pixellist' option or ind2sub
  1 Comment
Andrei Bobrov
Andrei Bobrov on 29 Jun 2011
+1
Hi Sean! I stupid, forgotten about the variable 4-connectivity. Thanks

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Paulo Silva
Paulo Silva on 29 Jun 2011
Just for fun
I=[1 1 0 0 0 0 0 0 0 0
0 0 1 1 0 0 0 0 0 0
0 0 0 0 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0];
up=[];down=[];
for c=1:size(I,2)
d=0;u=1;
for r=1:size(I,1)
if(d==1)
down=[down sub2ind(size(I),r,c)];
end
if(I(r,c)==1)
d=1;u=0;
end
if u==1
up=[up sub2ind(size(I),r,c)];
end
end
end
disp('index of zeros bellow the 1')
down
disp('index of zeros above the 1')
up
%for big arrays it's better to pre-allocate the up and down vectors, much faster
  1 Comment
Mohammad Golam Kibria
Mohammad Golam Kibria on 30 Jun 2011
Thanks. Its also ok.How to pre-allocate the up and down vectors?

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