[Help] with randomizing a Permutation

I created an emotion recognition paradigm which shows 144 short video clips of emotional faces.

• 1-36 angry faces
• 37-72 fearful faces
• 73-108 sad faces
• 109-144 neutral faces

I could need help in randomizing those video clips with the restriction that the same emotion is not shown more than 3 times consecutively. In the end I want a randomized numerical sequence containing all numbers from 1 to 144. Each number only shown once.

I'm glad for any help!

Answer 1

[Sai Veeramachaneni]

You can use below function to achieve behavior you need.

function sans = getIds()
    emotions = zeros(1,144);
    emotions=string(emotions);
    for i=1:36
        emotions(i)="angry";
    end
    for i=35:72
        emotions(i)="fear";
    end
    for i=73:108
        emotions(i)="sad";
    end
    for i=109:144
        emotions(i)="neutral";
    end
    sans=1:144;%final answer is stored in this
    sequence=1:144; %temporary sequence
    pointer=144;
    i=1;
    while i<=144
        tem = randi([1,pointer],1);
        temp = sequence(tem);
        if (i>3 && (emotions(sans(i-1))~=emotions(temp) ||...
                emotions(sans(i-2))~=emotions(temp) ||...
                emotions(sans(i-3))~=emotions(temp)))|| i<=3
            sans(i)=temp;
            i=i+1;
            [sequence(tem),sequence(pointer)]=deal(sequence(pointer),sequence(tem));
            pointer=pointer-1;
        end
    end
end