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number of elements of each unique values in a matrix

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Christopher
Christopher le 15 Oct 2014
Commenté : Sean de Wolski le 15 Oct 2014
I can use unique(A) to get an array of each unique value in the matrix A. However, how can I also get an array of the number of elements with each unique value? For instance
B=unique(A) might give:
[1; 4; 6; 8];
and an additional step might give:
[10; 1; 5; 7];
if there were 10 entries of 1, 1 entry of 4, 5 entries of 6, etc.
I know I can easily do this by doing find(A==B(1,1))... etc. but if the array of uniques is long then this should be very inefficient.
Is there a function like unique which returns the number of elements for each unique value without much additional computation??
Thanks

Réponse acceptée

Andrei Bobrov
Andrei Bobrov le 15 Oct 2014
B = unique(A);
out = [B,histc(A,B)];
  3 commentaires
Sean de Wolski
Sean de Wolski le 15 Oct 2014
It should be, Christopher.
Sean de Wolski
Sean de Wolski le 15 Oct 2014
A = [1;1;1;2;3;3];
B = unique(A);
out = [B,histc(A,B)]
out =
1 3
2 1
3 2
First column is value, second is number of occurrences

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