How to count the number of consecutive repetitions of an array?

Hi everybody,

I have a double array or a logical one made like this above: A=[0 1 1 1 0 0 1 0 1 1 0 0 0 1 0 1 1 1]; And I would like to count the number of consecutive repetitions of values 1, getting as output an array like this: B=[3 1 2 1 3], where 3=3 times 1; 1=1 time 1; ecc.. Please, can someone help me with this issue?

Thanks a lot!

Answer 1

[James Tursa]

E.g.,

[r,s] = runlength(A,numel(A));
result = r(logical(s));

You can find runlength on the FEX:

https://www.mathworks.com/matlabcentral/fileexchange/241-runlength-m

[giovanni negro]

Thanks so much! Works perfectly!

[Lucademicus]

Hi James, what is the reason of the second line of your answer, r(logical(s))? I have tested your answer but r(logical(s)) seems redundant.

[Walter Roberson]

The original poster indicated

I have a double array or a logical one made like this above: A=[0 1 1 1 0 0 1 0 1 1 0 0 0 1 0 1 1 1];

Therefore sometimes the input will be double even if it only contains 0 and 1. In that case, the s that is output would be double, and indexing at double 0 is not permitted.

[Lucademicus]

Thank you for the clarrification Walter, I should have read more carefully.

[Ved Prakash]

I am not getting the required output instead only ones are coming in result. Please help me with this.

result= [1 1 1 1 1......1498 times ]

whereas my input is attached

[Walter Roberson]

Your A vector contains values between 1 and 235, not the 0 and 1 of the original Question. What is it that you want to compute on your A?

[Walter Roberson]

Your A vector has no runs at all. Every value that occurs, occurs in isolation, with there never being two of the same value in a row. You cannot do any useful run-length encoding on it -- not unless you are able to go into pairs of values instead of single values.

load a.mat
results = {};
for targ = unique(A).'
   a = A.' == targ;
   starts = strfind([0 a], [0 1]);
   if isempty(starts); continue; end
   stops = strfind([a 0], [1 0]);
   results{end+1, 1} = [targ, stops - starts + 1];
end
celldisp(results)