number of elements of each unique values in a matrix

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Christopher 2014-10-15

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评论： Sean de Wolski 2014-10-15

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

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采纳的回答

Andrei Bobrov 2014-10-15

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https://ww2.mathworks.cn/matlabcentral/answers/158677-number-of-elements-of-each-unique-values-in-a-matrix#answer_155216

在 MATLAB Online 中打开

B = unique(A);
out = [B,histc(A,B)];

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Sean de Wolski 2014-10-15

It should be, Christopher.

Sean de Wolski 2014-10-15

在 MATLAB Online 中打开

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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