create vector of repeating elements (sort of)

How can I easily create a vector such that:

w = 3

n = 8

v = (1 w times) (2 w times) (3 w times) ... (n w times)

so i would have:

v = [1 1 1 2 2 2 3 3 3 4 4 4 .... 8 8 8]

Answer 1

[the cyclist]

Here is one way:

w = 3;
n = 8;

v = repmat(1:n,[w 1])
v = v(:)'

[HC Song]

brilliant

Answer 2

[Lucas García]

One of many ways:

>> w = 3; n = 8;
>> v = repmat(1:n,w,1);
>> v = v(1:end)

Answer 3

[Oleg Komarov]

For variable w use rude from the fex:

rude(len,val)

Answer 4

[Richard Tyson]

If you need it to be fast you should avoid using repmat. Stick to C functions which don't need to parse input arguments and do one specific task:

n = 8;

w = 3;

v = ceil( [1:(w*n)]./w )

If anyone has a faster way please post. I do this kind of operation a lot.

[the cyclist]

This thread is nearly two years old. You might want to post this as a new question.

[Artur Palha]

n = 8; w = 3; v = rectpulse(1:n)

This is the fastest option I know of.

Answer 5

[Wayne King]

One way:

    w = 3;
    x = 1:8;
    x = arrayfun(@(x) repmat(x,1,w),x,'UniformOutput',false);
    x = cell2mat(x);

Wayne

[Jan]

ARRAYFUN and CELL2MAT needs a lot of time. Using REPMAT directly is much faster.