MATLAB: How to constructing a matrix of repeated rows v

indexingmatrix arraymatrix manipulation

If I have an arbitrary matrix A and a row vector v of 1 row and the same number of columns as A.
Suppose I want to construct a matrix Q of the same size as A where every row in Q is the vector v.
Illustrative example:
A=[ 1 1 1; 2 2 2; 3 3 3; 4 4 4]; v=[5 5 5];
%I want to create Q s.t
Q=[5 5 5; 5 5 5 5; 5 5 5 5; 5 5 5 5];
Thanks

Best Answer

Either of the following would work
>> Q=repelem(v,size(A,1),1)
>> Q=repmat(v,size(A,1),1)
but note that it's not normally something you need or want to do. Matlab has deliberately provided implicit expansion,
https://nhigham.com/2016/09/20/implicit-expansion-matlab-r2016b/
or for older Matlab versions bsxfun,
https://www.mathworks.com/help/matlab/ref/bsxfun.html
to avoid such copying in many common situations.
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