I have matrix
A = [1;2;3]
How do I replicate A four times, replicating each row four times before moving onto the next, to get
[1;1;1;1;2;2;2;2;3;3;3;3;4;4;4;4]
?
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Robert Seifert
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user1956609
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1A fairly comprehensive list comparing many solutions to this problem can be found here: http://stackoverflow.com/questions/14615305/a-similar-function-to-rs-rep-in-matlab – Dan Jan 14 '14 at 06:45
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Note since 2015a the best method is to use the builtin [`repelem`](http://www.mathworks.com/help/matlab/ref/repelem.html) function – Dan Jun 02 '16 at 14:10
2 Answers
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In this particular instance, you could do something along the lines of
A = [1;2;3;4];
B = repmat(A',4,1);
B = B(:);
What this does is replicate A' to create a matrix B:
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
It then converts it to a single column using B(:).
MrAzzaman
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How about using kron? It's perfect for this.
kron(A,ones(4, 1))
Stewie Griffin
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the `repmat` solution turns out to be more efficient than `kron` (http://stackoverflow.com/questions/14615305/a-similar-function-to-rs-rep-in-matlab/14620028#14620028) and imo more intuitive too – Dan Jan 14 '14 at 06:25
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2@Dan: "intuitive": that depends on what world you're from. To mathematicians, `kron` rings more bells than `repmat`. – Rody Oldenhuis Jan 14 '14 at 06:43
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@RodyOldenhuis true, that's why I said in my opinion. Maybe I should have said from my perspective rather. – Dan Jan 14 '14 at 06:44
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