Question about logical calculation in matrix

I want to sum up the numbers on the 1st column if its corresponding numbers on the 2nd column =1; and if sum up the numbers on the 1st column if its corresponding numbers on the 2nd column =2; The answer should be r1=0.5 r2=1.4 I don't know where I made mistakes. Here is the code I have so far. PLEASE HELP ME OUT。

AA=[0.2 1;0.3 1;0.5 2;0.9 2];  
for i = 1:4
       if AA(i,2)<2
          r1=zeros(1);
          r1=r1+AA(i,1);

        else
            r2=zeros(i,1);
            r2=r2+AA(i,1)

        end
    end

Answer 1

[Jan]

The mistake is the zeros inside the loop, which resets the counter repeatedly:

AA = [0.2 1; 0.3 1; 0.5 2; 0.9 2];  
r1 = 0;   % BEFORE the loop
r2 = 0;
for i = 1:4
  if AA(i,2)<2
    r1 = r1 + AA(i,1);
  else
    r2 = r2 + AA(i,1);
  end
end

Or smarter without a loop:

match = (A(:, 2) == 1);
r1    = sum(A(match, 1));
r1    = sum(A(~match, 1));

Answer 2

[Stephen23]

Just use accumarray:

>> AA = [0.2,1;0.3,1;0.5,2;0.9,2]
AA =
   0.20000   1.00000
   0.30000   1.00000
   0.50000   2.00000
   0.90000   2.00000
>> accumarray(AA(:,2),AA(:,1))
ans =
   0.50000
   1.40000
>>