Keep a tally of the number of occurences of a value in an array

Hello,

I have an array with integers from 1 to n. I would like to create a second array with the occurence number of the value in the corresponding location (index) of the initial array. For instance, if I have a first array [2 3 1 2 1 4 3 2 4], I want to generate a second array [1 1 1 2 2 1 2 3 2].

I'd like to avoid a series of n conditional statements.

Thx!

[Jiri Hajek]

Hi, you don't need conditional statements, but a loop is probably necessary... You can use logical indexing:

LogicalIndexes = FirstArray == i;
SecondArray(LogicalIndexes) = nnz(LogicalIndexes);

Answer 1

[Stephen23]

A = [2,3,1,2,1,4,3,2,4];
% method 1
F = @(n)nnz(A(1:n)==A(n));
B = arrayfun(F,1:numel(A))

B = 1×9

1 1 1 2 2 1 2 3 2

% method 2
B = sum(triu(A==A.'),1)

B = 1×9

1 1 1 2 2 1 2 3 2

[FredMat]

Thanks, method 2 works great. I cannot believe how simple the solution was.