Exchange position of elements in an array

Hi given two arrays

SP =  [1 2 3 4 8 11 13 14 15 16 18 19 20];
Y= [24 18 18 18 18 18 18 18 18 18 18 18 18];

I create an array

S= [19	1	4	14	20	11	20	13	18	11	8	16	14	13	3	13	8	1	15	13	16	14	1	11	3	4	20	19	8	20	14	18	3	11	13	13	11	20	11	20	16	2	20	15	1	11	4	13	18	20	3	15	11	8	16	8	14	14	1	8	14	8	1	16	3	20	8	18	16	4	15	2	8	2	3	16	14	3	15	2	1	18	13	4	18	4	20	18	14	4	2	2	2	4	8	11	20	13	3	11	16	19	2	18	3	11	19	1	13	3	19	11	15	3	14	19	16	2	8	13	3	11	20	19	18	18	19	15	14	16	8	1	3	18	18	4	14	15	15	18	1	3	4	1	15	2	11	1	16	15	8	13	16	16	1	19	16	13	19	8	19	11	20	1	15	2	13	14	20	1	2	8	14	4	15	15	4	1	1	3	18	1	4	4	1	8	11	2	1	18	14	18	13	8	14	19	3	18	11	4	11	20	16	1	15	15	19	2	19	3	2	20	13	19	4	13	15	4	16	1	8	19	1	3	19	16	2	4	14	2	14	1	16	19	15	20	2	20	13	18];

Where 1 is repeated 24 times, 2 is repeated 18 times, 3 is repeated 18 times and so on. So the array SP tells us the diversity of elements and Y how many times they are repeated in S.

Now what I want to do is to exchange randomly the position of the elements inside S.

In particular I want to follow two rules:

1) Just some elements can exchange with eachother. In particular considering the matrix BB

BB= [1 2  3  4  0   11  14  15;
    0  0  0  8  13  16  0   0;
    0  0  0  0  0   18  0   0;
    0  0  0  0  0   19  0   0;
    0  0  0  0  0   20  0   0];

We can exchange each other just the element on the same column. It means that a 11 can just exchange with 16,18,19,20. While 4 can just exchange with 8. Obviously if there is just one number on the columns it will remain in its position.

2) I want that the elements exchange their position randomly with the one on the same columns of BB. But I don't want to substitute a value with another random value on the same colums! This means that at the end, the number of repetitons indicated in Y will be respected in the new array

May someone can help me with this code?

Answer 1

[David Hill]

for i=1:size(BB,2)
    x=S(ismember(S,BB(:,i)));
    S(ismember(S,BB(:,i)))=x(randperm(length(x)));
end