hi every one ,

A=[ 1 1 1 2 2 3 3 3 1 1 4 4 4 2 2 3 3 3 4 3 ]

how can i count the number of 1 and 2 and 3 and 4 in the row vector

thank u

Answer 1

[Alex Mcaulley]

sum(A==1) % or sum(A==2)...

[Adam Danz]

Note that you'll need to calculate the unique values in A and then loop through each of them in order to use this method.

Aunq = unique(A); 
count = zeros(size(Aunq));
for i = 1:length(Aunq)
    count(i) = sum(A==Aunq(i)):
end

...which is all done in the one line of code I propsed using histcounts().

Answer 2

[Adam Danz]

Use histcounts() instead. It's designed for this purpose.

A=[ 1 1 1 2 2 3 3 3 1 1 4 4 4 2 2 3 3 3 4 3 ];

counts = histcounts(A,[unique(A),max(A)+1]); 

Result

list = table(unique(A)', counts', 'VariableNames', {'Number', 'Count'}); 

list =
    4×2 table
    Number    Count
    ______    _____
      1         5  
      2         4  
      3         7  
      4         4