Count repetitions separately in an array

I have this array

A = [1;1;2;2;2;2;2;2;3;1;1;1;1;4;4;4;1;1;1;5;5];

I want Matlab to tell me when the repetition of 1 is greater than 2 for example, but I don't know any function that does this.

Could you help ? Thanks a lot !

[Lea Martine Francoise]

For example, I want Matlab to tell me the position in my vector of where I have 4 ones in a row for example which here would be indices 10 to 14

Answer 1

[Stephen23]

A = [1;1;2;2;2;2;2;2;3;1;1;1;1;4;4;4;1;1;1;5;5];
D = diff([0;A;0]==1);
B = find(D>0);
E = find(D<0);
L = E-B

L = 3×1

2 4 3

X = find(L>2);
B(X) % start indices

ans = 2×1

10 17

E(X)-1 % end indices

ans = 2×1

13 19

[Lea Martine Francoise]

I think that would be perfect but how do I get the end indices also ? Because I want to fill those indices with NaN. For example for a condition when I have 6 ones in a row, I want to replace them by NaN

[Lea Martine Francoise]

Thank you very much !!

Answer 2

[Antoni Garcia-Herreros]

Hello Lea,

Try something like this:

% Where 1 would be the number you are looking and 2 the number of repeats
sum(A==1)>2 % True if there are more than two instances of 1 in your array

[Lea Martine Francoise]

Yes but I guess this does not give me the indices of where I have for example 5 ones in a row and this is what I am looking for :)