Randomize / Shuffle function with order (no subsequent repetition) constraint

Hello, I am using MATLAB 2016b and I am looking to write a matlab function that randomizes / shuffles a matrix with some constraints.

Specifically, the input for this function would be a 10*1 matrix with the following content: [1;2;3;4;5;6;7;8;9;10]. Next I would like to have a variable (lets call it X) that specifies the amount of repetitions and therefore indicates the dimensions of the output matrix (see further for more clarification)

The wanted output is a X*1 matrix, with X being a multiple of 10 (e.g., 20*1, 30*1, 40*1, etc), based on the X variable that I discussed previously.

The goal is to randomize and shuffle the input matrix, and save this output to another matrix. The output matrix needs to satisfy the following constraints: - Every number from the input matrix needs to be equally present in the output matrix. So for example, if the output matrix is specified to be 20*1, every number needs to be present twice in the output matrix, and so on. - No more than two consecutive repeats from the same number are allowed in the output matrix. Thus, for example 2;2;3 is allowed, but not 2;2;2

I hope someone can and wants to help me in this quest. Thanks in advance

Answer 1

[Guillaume]

Your requirements seem fairly simple. The only difficult one is the requirement that there be no more than two identical consecutive numbers. I' d just keep generating permutations until that's the case:

%inputs
v = 1:10;    %input vector of different numbers
x = 5;       %number of repetitions

out = repelem(v, x);  
out = out(randperm(numel(out)));  %1st try
while ~isempty(strfind(diff(out), [0 0]))  %diff(out) will have at least two consecutive 0 if there are 3 or more identical consecutive numbers
     out = out(randperm(numel(out)));  %try again
end