How to count iterations of an element in a column according to elements in another column?

Hello,

Attached you find a matrix I'm working with in R2012a. Column 1 corresponds to participant ID, 2 corresponds to questions, 3 to responses. Step 1: I am interested in finding a way to count how many times each question in column 2 was given a response of 1 or 2 OR 5 or 6 in column 3 (is there such a thing as a 'count' function?) Step 2: I am interested in putting the results of step 1 in another 49x3 matrix in which column 1 will correspond to question number, column 2 the number of times each question was given a response of 1 or 2 and column 3 the number of times each question was given a response of 5 or 6 across all participants (that is, ignore column 1 of hh.mat).

I can think of ways of doing this but I am stuck. I know I have to create a for loop that goes through each and every one of the 49 values in column 2. I know that I will have to create 2/more if statements (1 statement corresponding to instances in which a value in column 2 was given a rating of 1 | 2 in column 3 and another one for instances in which a value in column 2 was given a rating of 5 | 6). I've been trying stuff around but I'm a bit lost. Could you please be so kind as to help?

Answer 1

[Andrei Bobrov]

d = unique(hh(:,2));
a = ismember(hh(:,3),1:2);
b = ismember(hh(:,3),4:5);
step1 = sum(a + b);
step2 = [d, accumarray(hh(:,2),a), accumarray(hh(:,2),b)];

[Bianca Elena Ivanof]

Excellent, Andrei!

The solution is so simple - my solution was a bit too complicated I guess, haha.

Many thanks!