# Counting frequency of occurrence in matrix

362 views (last 30 days)
Guan Zhao on 23 Oct 2012
Commented: Brian Derstine on 31 Aug 2021
Good day,
I am attempting to count the number of times each number in a matrix occurred in the matrix.
For example, suppose I have a matrix;
x =
22 23 24 23
24 23 24 22
22 23 23 23
I want an output which will tell me 22 occurred 3 times, 23 occurred 6 times, and 24 occurred 2 times. The actual matrix is larger in size.
Is there a specific function which returns such values or are there any other ways I can resolve this challenge?
m_vdv on 10 May 2018
Hi, is it also possible to do this without using 'unique' and 'sort'? For example with only using a for loop and/or if loop? Thanks in advance.

Andrei Bobrov on 23 Oct 2012
x =[
22 23 24 23
24 23 24 22
22 23 23 23];
a = unique(x);
out = [a,histc(x(:),a)];
Brian Derstine on 31 Aug 2021
would be nice if you could just do tabulate(x)

Aurelien Queffurust on 23 Oct 2012
Using nnz for example:
nnz(x==22)
will return 3
Guan Zhao on 23 Oct 2012
Hi,
My actual matrix will have at least 256 elements. I will have to consider zero elements too.
Regards
Guan Zhao

Thomas on 23 Oct 2012
x=[22 23 24 23
24 23 24 22
22 23 23 23];
[a,b]=hist(x,unique(x));
out=[b' sum((a),2)]

abdelrahim hashem on 15 Nov 2017
x = [22 23 24 23; 24 23 24 22; 22 23 23 23];
un_x = unique(x);
for i = 1:length(un)
un(i), length(find(x == un_x(i)))
end

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