MATLAB: Duplicating rows in a matrix

arraymatrix

Hi there
I have a matrix that i need to make twice as long. i.e i need to double the length of columns. eg i need: 
[0 1 0 0]
[0 2 0 0]
to become:
[0 1 0 0]
[0 1 0 0]
[0 2 0 0]
[0 2 0 0]
Thanks

Best Answer

Try this: 
M = [0 1 0 0
     0 2 0 0];
M2 = repmat(M, 1, 2);
M2 = reshape(M2', [], 4)'
producing: 
M2 =
     0     1     0     0
     0     1     0     0
     0     2     0     0
     0     2     0     0
You could combine both calculations into a one-line calcualtion if you want to.
EDIT —
Generally, for ‘N’ repitions, the code becomes: 
N = 4;                                  % Number Of Repititions
Mn = repmat(M, 1, N)
Mn = reshape(Mn', [], 2*N)'
producing: 
Mn =
     0     1     0     0
     0     1     0     0
     0     1     0     0
     0     1     0     0
     0     2     0     0
     0     2     0     0
     0     2     0     0
     0     2     0     0
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