Combining the matrix' values

is there any predefined function let us to combine the values in a matrix example: let A the original matrix

if true
                        A= 1 2 
                           4 5 
                           7 8
end 
the result that i'm loking for is 

if true
                                C= 1 1 1 1 2 2 2 2 
                                   4 4 5 5 4 4 5 5
                                   7 8 7 8 7 8 7 8
end

[James Tursa]

You need to supply a LOT more detail about what the rules are for generating C from A. Otherwise we are left with too much guesswork. E.g., this works given what you have posted so far, but I am pretty sure it isn't what you want:

if( isequal(A,[1 2 3 4 7 8]) )
    C = [1 1 1 1 2 2 2 2 4 4 5 5 4 4 5 5 7 8 7 8 7 8 7 8];
end

[James Tursa]

So you want the columns of C to be all possible combinations of the elements of the rows of A?

[dpb]

Appears he's dividing the two values into 1/2^n groupings where n=1:nRows. That is the first new row is 2 subsets, the 2nd is 4, etc., ...

That said, other than coding a loop and repmat no magic solution leaps out at me at the moment...

Answer 1

[James Tursa]

C = allcomb(A(1,:),A(:,2),A(:,3))'

You can find allcomb (by Jos) on the FEX:

http://www.mathworks.com/matlabcentral/fileexchange/10064-allcomb

Or more generally,

B = mat2cell(A,ones(1,size(A,1)),size(A,2));
C = allcomb(B{:})';

Answer 2

[Roger Stafford]

I think the following generalizes what you have requested for a matrix, A, of arbitrary size:

   [m,n] = size(A);
   [J,I] = meshgrid(0:n*2^(m-1)-1,m-1:-1:0);
   C = A(m*(mod(floor(J./2.^I),n)+1)-I);