Concatenate vector in a 3d matrix

Hi. I have these vectors: a = [11 12 13 14]; b = [21 22 23 24]; c = [31 32 33 34]; d = [41 42 43 44];

I want to concatenate them in a 2x2x4 matrix: M(:,:,1) = [11 21; 31 41]; M(:,:,2)= [12 22; 32 42]; and so on.

How can I do that?

Answer 1

[James Tursa]

For your exact problem:

M = reshape([a;c;b;d],2,2,4);

Then generalize as appropriate. E.g., if a,b,c,d are not row vectors to start with,

M = reshape([a(:)';c(:)';b(:)';d(:)'],2,2,4);

etc.

[Alessandro Masullo]

Perfect! Thank you!

But now I have another problem...

I have two matrices

M = (3 by 3 by 50)

V = (3 by 1 by 50)

The third dimension is the time.

I want the result of M*V, as a product (3 by 3) * (3 by 1) for each time step.

Neither * nor .* has worked :(

[Thomas]

Will this work?

for i=1:50

pr(:,:,i)=M(:,:,i)*V(:,:,i);

end

[Alessandro Masullo]

I would like to avoid cycles... :)

[James Tursa]

MtimesV = mtimesx(M,V,'speed');

You can find mtimesx on the FEX here:

http://www.mathworks.com/matlabcentral/fileexchange/25977-mtimesx-fast-matrix-multiply-with-multi-dimensional-support