Element-wise array replication in Matlab
I'm a fan of the KRON function:
>> a = 1:3;>> N = 3;>> b = kron(a,ones(1,N))b = 1 1 1 2 2 2 3 3 3You can also look at this related question (which dealt with replicating elements of 2-D matrices) to see some of the other solutions involving matrix indexing. Here's one such solution (inspired by Edric's answer):
>> b = a(ceil((1:N*numel(a))/N))b = 1 1 1 2 2 2 3 3 3
a = [1 2 3];N = 3;b = reshape(repmat(a,N,1), 1, [])
As of R2015a, there is a built-in and documented function to do this, repelem:
repelemReplicate elements of an array.
W = repelem(V,N), with vectorVand scalarN, creates a vectorWwhere each element ofVis repeatedNtimes.
The second argument can also be a vector of the same length as V to specify the number of replications for each element. For 2D replication:
B = repelem(A,N1,N2)No need for kron or other tricks anymore!
UPDATE: For a performance comparison with other speedy methods, please see the Q&A Repeat copies of array elements: Run-length decoding in MATLAB.