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?
Solution 1:
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.
Solution 2:
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);
Solution 3:
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)