Repeat numbers of X based on Y to produce Z

I have 2 matrices, X and Y, and using these 2 matrices I would like to produce a third one called Z.

X = [1; 2; 3; 4; 5;]
Y = [3; 1; 4; 2; 2;]

where in Z, the numbers in X are repeated based on X

Z = [1;
    1;
    1;
    2;
    3;
    3;
    3;
    3;
    4;
    4;
    5;
    5;]

Answer 1

[Star Strider]

Use the repelem function (R2015a and later):

Z = repelem(X, Y)

producing:

Z =
     1
     1
     1
     2
     3
     3
     3
     3
     4
     4
     5
     5

[JL]

Thanks!

[Star Strider]

As always, my pleasure!

Answer 2

[John D'Errico]

help repelem