Changing matrix into order pairs

Hi, I have a matrix A=[1 2;1 3; 2 1;5 6;1 7;6 7],how I can change 'A' like this A=[(1 2);(1 3);(2 1);(5 6);(1 7);(6 7)] or like this A=[[1 2];[1 3];[2 1];[5 6];[1 7];[6 7]]. Thanks in advance

Answer 1

[Guillaume]

Neither of the two examples you show are remotely valid syntax in matlab since a matrix can only store a single scalar number per element, not matrices. So it's a bit difficult to answer you. Perhaps you want a cell array A = {[1 2];[1 3];[2 1];[5 6];[1 7];[6 7]} since cell arrays allow you to store matrices in each cell. In which case,

A = [1 2; 1 3; 2 1; 5 6; 1 7; 6 7]
newA = num2cell(A, 2)

But the bigger question is why? There's nothing that you can do with the cell array that you couldn't do with the original matrix (and probably more simply).

Answer 2

[Alexandra Harkai]

This gives what you described as [[1 2];[1 3];[2 1];[5 6];[1 7];[6 7]]:

 A=[1 2;1 3; 2 1;5 6;1 7;6 7];
 B = mat2cell(A, ones(1,6),2);

But, it is not exactly clear what you mean by 'order pairs' or what you mean by [(1 2);(1 3);(2 1);(5 6);(1 7);(6 7)]. What is it you exactly want to do with these 'pairs'? For example, if you just want to access the n-th pair at a time, you can instead simply write

 A(n,:)

[Guillaume]

If you're going to use mat2cell to convert all the rows into a cell array (instead of the simpler num2cell), at least don't hardcode the sizes:

B = mat2cell(A, ones(1, size(A, 1)), size(A, 2));

so that it works with A of any size.

Like you, I suspect we've got a case of XY problem where the real question is yet to be asked.

[Alexandra Harkai]

Couldn't agree more.

Answer 3

[Amir Afshar]

I think what you want is to have each entry in a vector be a pair of elements. To do that, you need to store each pair in a cell:

B = cell(numel(A,1),1);
for i = 1:length(A)
    B(i) = {A(i,:)};
end

Then if

A = [1 2; 1 3; 2 1; 5 6; 1 7; 6 7];

Using the above snip of code:

B = 1×3 cell array

    {1×2 double}    {1×2 double}    {1×2 double}

To access a specific element in B, though, you need to use {}.

B{1} returns [1,2]. B{1,2} still gives [1,2], so in order to get the second element from the first pair, you need to do something clever, like (using the dot product with a unit basis vector to extract the second element):

B{1}*[0;1]

This returns 2. As another example, B{4} returns [5,6], but B{4}*[1;0] gives 5:

B{4}*[1;0]

ans =

     5