How to reshape a matrix in a specific way?

If I have a matrix (A) that is 10x4, how would I reshape this matrix to be a new 5x8 matrix (B) so that the first two rows of A are concatenated to be the first row of B, the 3rd and 4th row of A were the second row of B etc.

Thanks in advance for your help

Answer 1

[Stephen23]

Just use reshape and transpose (where 8 is the required number of columns):

>> A = rand(10,4); % fake data
>> B = reshape(A.',8,[]).';

and checking:

>> A(1:2,:)
ans =
   0.42279   0.17374   0.11111   0.86420
   0.25314   0.46765   0.14823   0.10467
>> B(1,:)
ans =
   0.42279   0.17374   0.11111   0.86420   0.25314   0.46765   0.14823   0.10467

In your case use (where 25536*72 is the required number of columns):

B = reshape(A.',25536*72,[]).';

[Ciaran Green]

Fantastic, makes perfect sense - thank you for your help.

Answer 2

[Fangjun Jiang]

A=reshape(1:40,10,4);
B=[A(1:2:10,:) A(2:2:10,:)]

[Ciaran Green]

OK so I gave the 10x4 etc as a simpler example. I am doing this for a 459648x72 matrix making every 25536 rows into one long row. Could you explain the second line? Would the code for the first line then be:

A=reshape(1:33094656,459648,72);

Thanks for your help

[Stephen23]

Fangjun Jiang used the first line to define some fake data: it defines a matrix A with size 10x4, just like you specified in your question but did not provide us with. There is nothing special about this matrix (it contains the values 1 to 40), and you certainly don't need this in your code as you apparently already have matrix A.

[Ciaran Green]

Oh, oops, makes sense - thank you for clarification.