Repeated Permutation of the same numbers

Hi everyone,

Say I have an array a of 3 numbers (or alternatively of 4 or 5 or..):

a = [0.21 0.018 0.34];

I want to create an array b, which only contains these numbers, however in random order, though each of the numbers should appear the same number of times. For instance if b is [30,1], I would want each of the three numbers to appear 10 times. I know the randperm function, but it seems to me that using randperm is not so straightforward for this task?

Many thanks

Answer 1

[Adam]

e.g. for a length 3, b length 30

idxA = repmat( 1:3, [1, 10] ); % Ensure each element appears same number of times
idxB = randperm( 30 );
idxA = idxA( idxB );

That will give you a random array of 10 each of 1s, 2s and 3s, indicating which of the 3 elements of a should be in each element of b. From there the rest is trivial.

Answer 2

[John D'Errico]

Surely this is no harder than creating a new vector, that has the numbers repeated as often as you wish, then randomly permuting it.

[MiauMiau]

Yes..somehow did not come to my mind. Thx though