Concatenate a 10x4x40 Double Matrix to 40x4

Hello,

I have a matrix A() that is 10x4x40. I would only like the first row of the matrix A(1,:,:) but want to vertically concatenate the data so it transforms into B() that is 40x4. How would I do this?

Right now I have tried doing

vertcat(A(:,:))

which returns a concatenated matrix of 1x160. Do I need to use a loop to do this? Please help!

Thank you

Answer 1

[Azzi Abdelmalek]

A=rand(10,4,40)
B=permute(A(1,:,:),[2 1 3])
out=B(:,:)'

[Roger Stafford]

@Azzi: Don't you mean

B=squeeze(permute(A(1,:,:),[1,3,2]));

Answer 2

[Fangjun Jiang]

reshape(A(1,:,:),40,[])

[Roger Stafford]

@Fangjun: When Matthew states that a 40 x 4 array is to be produced, I believe it implicit in this statement is the assumption that what were 40-element sequences along the 3rd dimension for a given row and column index are to be preserved in the columns of the resulting 40 x 4 array. However 'reshape' will not accomplish this. To take a simpler case suppose

A = [1 2 3  4  5  6;
     7 8 9 10 11 12];

We would like a 6 x 2 array B to be:

B = [1 7;
     2 8;
     3 9;
     4 10;
     5 11;
     6 12]

where the former rows become the columns. However B = reshape(A,6,2) will give:

   B = [1  4;
        7 10;
        2  5;
        8 11;
        3  6;
        9 12]

In other words 'reshape' would break up the sequences 1,2,3,4,5,6 and 7,8,9,10,11,12. I don't think Matthew would like that as applied to the 40-element columns of the result.

However, this would work:

B = squeeze(A(1,:,:)).';