maximizing efficiency in simple commands

I have an array given by

x = [1 2 3 4];

I would like to create a matrix that looks like

M = [1 2 3 4;
     1 2 3 4;
     1 2 3 4;
     1 2 3 4];

What's the most computationally efficient way to create M from x?

Answer 1

[Azzi Abdelmalek]

x=[1 2 3 4]; 
M=repmat(x,4,1)

[Walter Roberson]

Equivalently but removing the error checking:

x=[1 2 3 4];
M = x([1 1 1 1],:);

Answer 2

[Andrei Bobrov]

ones(4,1)*x

kron(ones(4,1),x)