Question

Say I have a matrix A with 3 columns c1, c2 and c3.

1 2 9
3 0 7
3 1 4

And I want a new matrix of dimension (3x3n) in which the first column is c1, the second column is c1^2, the n column is c1^n, the n+1 column is c2, the n+2 column is c2^2 and so on. Is there a quickly way to do this in MATLAB?

Answer 1

Combining PERMUTE, BSXFUN, and RESHAPE, you can do this quite easily such that it works for any size of A. I have separated the instructions for clarity, you can combine them into one line if you want.

n = 2;
A = [1 2 9; 3 0 7; 3 1 4];
[r,c] = size(A);

%# reshape A into a r-by-1-by-c array
A = permute(A,[1 3 2]);

%# create a r-by-n-by-c array with the powers
A = bsxfun(@power,A,1:n);

%# reshape such that we get a r-by-n*c array
A = reshape(A,r,[])

A =

     1     1     2     4     9    81
     3     9     0     0     7    49
     3     9     1     1     4    16