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

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MathWorks Support Team
on 11 Jan 2012

Commented: Walter Roberson
on 26 Apr 2022

I would like to be able to return the count of occurences of each element in a vector.

For example if I have a vector:

x=[10 25 4 10 9 4 4]

I expect the result to be

y=[2 1 3 2 1 3 3].

### Accepted Answer

MathWorks Support Team
on 27 Feb 2020

Edited: MathWorks Support Team
on 27 Feb 2020

As of MATLAB R2019a, you can use the “groupcounts” function to compute the number of times an element appears in a vector as a summary. In other words, the elements of the below output “GC” are the counts of the corresponding element values in “GR” (from the original input vector “x”):

x = [10 25 4 10 9 4 4]';

[GC,GR] = groupcounts(x)

GC =

3

1

2

1

GR =

4

9

10

25

For more information on "groupcounts", please see the documentation link below:

---

As of MATLAB R2018b, you can use the “grouptransform” function if you want to compute the number of times an element appears in a vector and output that count for each corresponding element of the input vector. For example:

x = [10 25 4 10 9 4 4]';

y = grouptransform(x,x,@numel)

y =

2

1

3

2

1

3

3

For more information on "grouptransform", please see the documentation link below:

---

Prior to MATLAB R2018b, while there is no single function to count occurrences of each element, there are a few ways to count elements in a vector:

1. Logical Indexing:

The following code snippet will give the desired output:

y = zeros(size(x));

for i = 1:length(x)

y(i) = sum(x==x(i));

end

For MATLAB R2016b and later, you can use implicit expansion to further simplify the code:

y = sum(x==x')

2. Binning:

You can use the "hist" and "unique" functions as shown here to do the same:

x = [10 25 4 10 9 4 4]

[a,b]=hist(x,unique(x))

3. Third-Party Tools:

For another workaround, see the following file, 'CountMember.m', that was contributed by a MATLAB user to do the same from a single function:

Note that MathWorks does not guarantee or warrant the use or content of submissions to the MATLAB Central File Exchange. Any questions, issues, or complaints should be directed to the contributing author.

##### 3 Comments

Walter Roberson
on 26 Apr 2022

https://www.mathworks.com/help/matlab/ref/double.groupcounts.html#mw_92fbcf5a-2ab5-45d0-ac09-68c1986c269f

when you use groupcounts then the groups are in the order returned by unique('sorted')

### More Answers (3)

Razvan Carbunescu
on 9 May 2019

>> x=[10 25 4 10 9 4 4]';

>> grouptransform(x,x,@numel)

ans =

2

1

3

2

1

3

3

>>[GC,GR]=groupcounts(x)

GC =

3

1

2

1

GR =

4

9

10

25

##### 4 Comments

Razvan Carbunescu
on 6 Jun 2019

Razvan Carbunescu
on 7 Jun 2019

Julian Hapke
on 1 Jun 2017

Edited: Julian Hapke
on 1 Jun 2017

here is another one:

sum(bsxfun(@eq,x,x'),1)

or if you want the output to be the same orientation as input

sum(bsxfun(@eq,x,x'),(size(x,2)==1)+1)

##### 1 Comment

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