Combinations of different rows of a matrix

I have a 90x2 matrix. I have to generate all combinations of 2 rows of the matrix. How can I do it?

Plz help

Answer 1

[Stephen23]

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

Answer 2

[Alex Mcaulley]

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),[]);

[Jess]

Sir

While executing the above code, the following error comes

Invalid expression.When calling a function or indexing a variable, use parantheses. Otherwise, check for mismatched delimiters

Plz help

[Alex Mcaulley]

If you execute the code as is it should work. Probably the problem is with your matrix

[Jess]

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]

Sir for 90x2 matrix, how should we do it?

Should we type all the elements first

Plz help