put random position set of number with conditional repeat

Question

I have this set of number a=[1 2 3]. And I want to put this number randomly into matrix 7 x 1, and number 1 must have 2 times, number 2 must have 3 times and number 3 must have 2 times. The sequence is not necessary. The answer look like. b=[1 2 2 2 1 3 3]'

Answer 1

Try randperm:

a=[1 2 3];
samps = [1 1 2 2 2 3 3]; % specify your desired repeats
samps = samps(randperm(numel(samps))); % shuffle them
b = a(samps)

Or, instead of specifying samps explicitly, you can specify the number of repetitions for each element of a and use arrayfun to compute samps:

reps = [2 3 2];
sampC = arrayfun(@(x,y)x*ones(1,y),a,reps,'uni',0);
samps = [sampC{:}];
samps = samps(randperm(numel(samps))); % shuffle them
b = a(samps)

Answer 2

%how often each value should occure
quantity=[2,2,3]
%values
a=[1,2,3]
l=[]
%get list of all values
for idx=1:numel(a)
 l=[l,ones(1,quantity(idx))*v(idx)]
end
%shuffle l
l=l(randperm(numel(l)))