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

采纳的回答

José-Luis
José-Luis 2014-5-23
编辑:José-Luis 2014-5-23
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.

更多回答(1 个)

Jos (10584)
Jos (10584) 2014-5-23
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 个评论
José-Luis
José-Luis 2014-5-23
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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