MATLAB: How to count and reduce values in matrix

arraycell arraysfor loopif statementMATLABmatrix manipulation

Matrix input:
input = [
1  3  50  60
1  1  40  60
1  4  30  60
2  3  40  50
2  4  30  50
2  1  50  50
2  9  10  50
3  2  20  0
3  9  30  0
3  5  40  0
4  2  50  -20
4  2  60  -20
4  1  10  -20
4  1  25  -20
4  8  80  -20
];
% there are three 1, so 60/3, there are four 2, so 50/4, there are three 3, so 0/3 and there are five 4, so -20/5. 
% 50-60/3 = 30
% 40-60/3 = 20
% 30-60/3 = 10
Based on the similar arrays in the first column, I want to find for example how many 1 are there. Then divide the forth column by that (for example 1 is 3 here) and then reduce the amount from the third column. The first output should be:
output1 = [
1  3  30
1  1  20
1  4  10
2  3  27.5
2  4  17.5
2  1  37.5
2  9  -2.5
3  2  20
3  9  30
3  5  40
4  2  54
4  2  64
4  1  14
4  1  29
4  8  84
];
For the second output, I want the same process, but instead of counting all same numbers in the first column, this time just look at the second column and count if there is 3 and 4 (for every unique number in the first column).
output2 = [
1  3  20
1  1  40
1  4  0
2  3  15
2  4  5
2  1  50
2  9  10
3  2  20
3  9  30
3  5  40
4  2  50
4  2  60
4  1  10
4  1  25
4  8  80
];
% for "1", there are two 3&4, so 60/2
% 50-60/2 = 20
% 30-60/2 = 0

Best Answer

a = input;
ii = accumarray(a(:,1),1);
out1 = [a(:,1:2),a(:,3) - a(:,end)./ii(a(:,1))];
t = ismember(a(:,2),3:4);
i1 = accumarray(a(:,1),t);
out2 = a(:,1:3);
out2(t,3) = out2(t,3) - a(t,end)./i1(a(t,1));
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