# Determining the number of occurrences of each unique element in a vector

How can I determine the relative frequency of a value in a MATLAB vector?

```vector = [ 2 2 2 2 1 1 1 2 2 1 1 1 2 2 2 2 1 2 ];
```

What function will return the number of occurrences of each unique element?

You can use unique in combination with histc to get the relative frequency.

```A=[1,2,3,1,2,4,2,1]; %#an example vector
unqA=unique(A);
```

This gives the unique elements as unqA=[1,2,3,4]. To get the number of occurances,

```countElA=histc(A,unqA); %# get the count of elements
relFreq=countElA/numel(A);
```

This gives countElA=[3,3,1,1] and relFreq=[0.3750, 0.3750, 0.1250, 0.1250], which is the relative frequency of the unique elements. This will work for both integers and floating points.

For the most general case where you have a vector of floating point values, you can use the functions UNIQUE and ACCUMARRAY:

```[uniqueValues,~,uniqueIndex] = unique(vector);
frequency = accumarray(uniqueIndex(:),1)./numel(vector);
```

You can use the function tabulate. See this example with your vector.

```vector = [ 2 2 2 2 1 1 1 2 2 1 1 1 2 2 2 2 1 2 ];
tabulate(vector);
Value    Count   Percent
1        7     38.89%
2       11     61.11%
```

If you need it in percent order, do:

```t = tabulate(vector);
t = sortrows(t, 3)
```

```unqV = unique(vector);
y = zeros(size(unqV));
for i = 1:length(unqV)
y(i) = sum(unqV(i)==vector);
end
```

unqV = [1 2] y = [7 11]