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Combinations of different rows of a matrix

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Jess
Jess 2019-6-19
回答： Stephen23 2019-6-20
I have a 90x2 matrix. I have to generate all combinations of 2 rows of the matrix. How can I do it?
Plz help

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采纳的回答

Stephen23
Stephen23 2019-6-20
Simpler using basic MATLAB indexing:
>> M = [1,5;6,2;5,6;7,5;9,0]
M =
1 5
6 2
5 6
7 5
9 0
>> X = nchoosek(1:size(M,1),2);
>> R = [M(X(:,1),:),M(X(:,2),:)]
R =
1 5 6 2
1 5 5 6
1 5 7 5
1 5 9 0
6 2 5 6
6 2 7 5
6 2 9 0
5 6 7 5
5 6 9 0
7 5 9 0

更多回答（1 个）

Alex Mcaulley
Alex Mcaulley 2019-6-19
A = rand(90,2); %Example
b = nchoosek(1:size(A,1),2);
res = reshape(cell2mat(arrayfun(@(i) A(b(i,:),:),1:size(b,1),'uni',0)),2,size(A,2),[]);
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Jess
Jess 2019-6-19
Sir
For example if I have a 5x2 matrix
1 5
6 2
5 6
7 5
9 0
Then my resultant matrix should be a 10 x 4 matrix with the following elements
1 5 1 5 (This should not come as it is repitition)
1 5 6 2
1 5 5 6
1 5 7 5
1 5 9 0
6 2 1 5 (This should not come as it is repitition)
6 2 6 2 (This should not come as it is repitition)
6 2 5 6
6 2 7 5
6 2 9 0
5 6 1 5 (This should not come as it is repitition)
5 6 6 2 (This should not come as it is repitition)
5 6 5 6 (This should not come as it is repitition)
5 6 7 5
5 6 9 0
7 5 1 5(This should not come as it is repitition)
7 5 6 2(This should not come as it is repitition)
7 5 5 6(This should not come as it is repitition)
7 5 7 5(This should not come as it is repitition)
7 5 9 0
9 0 1 5(This should not come as it is repitition)
9 0 6 2(This should not come as it is repitition)
9 0 5 6(This should not come as it is repitition)
9 0 7 5(This should not come as it is repitition)
9 0 9 0(This should not come as it is repitition)
Kindly help me with this
Jess
Jess 2019-6-20
Sir for 90x2 matrix, how should we do it?
Should we type all the elements first
Plz help

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