Create a vector with the number of repetitions

Hello, I wouldlike to create a vectorwith the number of repititions of a number for example, I have this data:

clear all
clc
data = [ 1 2004 3 5;
         2 2004 7 2;
         1 2005 9 4;
         2 2005 6 5;
         3 2005 3 7;
         4 2005 8 2] % Where data(:,1) is id and data(:,2) is year.

I would like to create a code that counts the numbers of id per year in a vector, just like this:

result = [2 2 4 4 4 4]';

thank you very much in advance.

Answer 1

[the cyclist]

I feel like there must be a better way, but this will work

data = [ 1 2004 3 5;
         2 2004 7 2;
         1 2005 9 4;
         2 2005 6 5;
         3 2005 3 7;
         4 2005 8 2 ] % Where data(:,1) is id and data(:,2) is year.

dataYear = data(:,2);
uniqueDataYear = unique(dataYear);
dataYearCount = histcounts(dataYear,[uniqueDataYear; Inf])

[~,loc] = ismember(dataYear,uniqueDataYear);

result = dataYearCount(loc)'

[Andes]

Great, thanks a lot!! it works great!