creating multi-dimensional arrays from vectors

Hi,

I want to create a multi-dimensional array 'b' from a vector 'a' as the following example:

a =

     1     2     3     4

b(:,:,1) =

     1     1
     1     1

b(:,:,2) =

     2     2
     2     2

b(:,:,3) =

     3     3
     3     3

b(:,:,4) =

     4     4
     4     4

Thus I want to copy each entry of 'a' as m by n (2 by 2 in the example) size matrices onto each level of 'b' along the third dimension. I need to avoid element-wise operations and be as fast as possible.

I would appreciate any help.

Thank you.

Answer 1

[Geoff]

[~,~,b] = ndgrid([0 0], [0 0], a)

[Pal]

Thanks! What are the tilde symbols? I have never seen them in Matlab syntax.

[Geoff]

They are a placeholder, meaning we don't care about a particular return value. It's the way to get the third return value into 'b' without assigning the first and second return values to a variable.

Answer 2

[James Tursa]

You can also see this related discussion:

http://www.mathworks.com/matlabcentral/answers/31594-multiply-each-element-of-a-vector-with-a-matrix