Generate automatically vectors of precise length and given values

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Hello
I want to automatically construct a vector of user defined size using a set of elements defined within a second vector by filling the 1st vector linearly.
As a small example
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
vector_2 = [1,100,2,100,3,100,4]
length_vector_1 = 12
% vector to be automatically generated
vector_1 = [1,100,2,100,3,100,4,100,1,100,2,100]
length_vector_1 = 3
% vector to be automatically generated
vector_1 = [1,100,2]
Is there a way to generate such vectors ?
Thanks in advance

Accepted Answer

José-Luis
José-Luis on 23 May 2014
Edited: José-Luis on 23 May 2014
vector_2 = [1,100,2,100,3,100,4];
numVal = 19;
your_vec = repmat(vector_2,1,ceil(numVal/numel(vector_2)));
your_vec = your_vec(1:numVal);
Please accept an answer if it helped you.

More Answers (1)

Jos (10584)
Jos (10584) on 23 May 2014
No need to create an intermediate vector with repmat that could be much longer than the final one. Just use simple indexing into the original vector:
vector_2 = [1,100,2,100,3,100,4];
length_vector_1 = 19;
vector_1 = vector_2(rem(0:length_vector_1 - 1, numel(vector_2))+1)
  2 Comments
José-Luis
José-Luis on 23 May 2014
Here's the trade-off:
vector_2 = rand(1,777777);
numVal = 100000000;
tic
your_vec = repmat(vector_2,1,ceil(numVal/numel(vector_2)));
your_vec = your_vec(1:numVal);
toc
vector_1 = vector_2(rem(0:numVal - 1, numel(vector_2))+1);
toc
Elapsed time is 3.062471 seconds.
Elapsed time is 5.132982 seconds.

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