How do I resize a matrix in MATLAB?

 Suppose I had a 1-by-12 matrix and I wanted to resize it to a 4-by-3 matrix. How could I do this?

My current solution is kind of ugly: 

for n = 1:(length(mat)/3)
    out(n,1:3) = mat( ((n-1)*3 + 1):((n-1)*3 + 3) );

Is there a better way to do this?  

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Answers: 
reshape is of course the proper solution, as stated by @gnovice.
A nice feature of reshape is that it allows this: 
 
 A = 1:12;
B = reshape(A,4,[]);
B =
     1     5     9
     2     6    10
     3     7    11
     4     8    12
So if you don't know how many columns there will be, reshape will compute it for you. Likewise, reshape will fill in the number of rows, if you leave that out.  
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