Generate automatically vectors of precise length and given values

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

Answer 1

[José-Luis]

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.

[Dimitris M]

Very nice answer ! Thanks

[José-Luis]

My pleasure

Answer 2

[Jos (10584)]

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)

[José-Luis]

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.

[Jos (10584)]

Indeed, my code is faster!

(You forgot to put a tic …)