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How can I count the occurrences of each element in a matrix in MATLAB?

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Tracy Campbell
Tracy Campbell on 25 May 2017
Answered: Geoff Hayes on 25 May 2017
I'm trying to figure out how to count how often certain numbers appear in a specific column of my matrix (each number is coded for a different category). Very new to MATLAB, any help is appreciated!

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Accepted Answer

Geoff Hayes
Geoff Hayes on 25 May 2017
Tracy - one way is to use ismemeber (though this can be "slow"). For example, suppose your column array is constructed as
c = randi(15, 25, 1); % so generate 25 random numbers from 1 to 15
m = [10 15]; % m is the set of integers that you trying to match on
sum(ismember(c,m))
Since ismember(c,m) returns a logical array of ones (indicating a match in m) and zeros (indicating no match) then we can sum up all the ones to determine how many elements of c are in m.
Note that the above is only valid for integers.

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