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# combining matrix rows with repeated elements

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Javad on 31 Jul 2014
Commented: Javad on 8 Aug 2014
I have a matrix which its some rows have one same elements. I want to combine this rows and save the result in a cell array without repeating the elements. What is the easiest way to do so? For example, I have
A = [1 2;3 4;2 5;5 6;4 7;8 9;10 9]
And want to get,
C = {[1 2 5 6],[3 4 7],[8 9 10]}
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Javad on 8 Aug 2014
Thanks for your point. I had a look at documentations which say u=A(ia) and A=u(ib), but I could not figure out how I can relate indices to separate them as I want. As a beginner, it's a little difficult for me to do this exercise!

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### Answers (1)

Jian Wei on 31 Jul 2014
If I understand it correctly, you are trying to cluster the vertices in a graph into different groups according to whether they are connected or not. For general cases, the problem might be nontrivial. Please try the following code to see if it generates the results you need.
% adjacency matrix
M = zeros(max(max(10)));
for k = 1:size(A,1)
M(A(k,1),A(k,2)) = 1;
M(A(k,2),A(k,1)) = 1;
end
flag = zeros(length(M),1);
C = cell(0);
for k = 1:length(M)
if flag(k)==0
p1 = k;
flag(k) = 1;
p2 = p1;
for ki = 1:length(p1)
node = p1(ki);
p2 = union(p2,find(M(node,:)==1));
end
while length(p2)~=length(p1)
p1 = p2;
p2 = p1;
for ki = 1:length(p1)
node = p1(ki);
p2 = union(p2,find(M(node,:)==1));
end
end
for ki = 1:length(p2)
flag(p2(ki)) = 1;
end
C{end+1} = p2;
end
end
C is the cell which contains different groups of vertices that are connected with each other.
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