Create vector with predetermined number of certain elements

Hi everyone,

I have a problem where I have a set of numbers, eg; [3 5 9] and for each of these numbers an amount of occurences eg. [2 1 5]. Now i would like to create a vector containing these numbers the prespecified amount of times, so for the example the result would be [3 3 5 9 9 9 9 9 ]. Is there an elegant way to do this in MATLAB, that is, vectorized?

Thanks in advance for your input.

Answer 1

[Star Strider]

Use the repelem funciton:

V = [3 5 9];
N = [2 1 5];
Out = repelem(V, N)

Out =
     3     3     5     9     9    9     9     9

[Bartdp]

Perfect ;), thanks for your answer.

[Star Strider]

My pleasure!

Answer 2

[Image Analyst]

Here's one straightforward, easy-to-understand way that's pretty fast.

numbers = [3 5 9];
occurrences = [2 1 5];
output = zeros(1, sum(occurrences));
index1 = 1;
for k = 1 : length(numbers)
  index2 = index1 + occurrences(k) - 1;
  output(index1:index2) = numbers(k)
  index1 = index2 + 1;
end

[Bartdp]

Thanks for your answer. I need to create such a vector several times within the body of a loop, and therefore making a lot of them. Do you have any idea on how to vectorize this code? Thanks in advance