matrix addition according to position vector
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Hello, i have matrix A wich is 2xn dimension and vector b that is 1xn. I want to sort and sum A acording to vector b. for explamle
A=[1 3 5 7 9 11;
2 4 6 8 10 12]
b=[1 1 3 4 5 3]
so answer would be
C=[4 0 16 7 9
6 0 18 8 10]
采纳的回答
A=[1 3 5 7 9 11;
2 4 6 8 10 12];
b=[1 1 3 4 5 3];
Maybe something like this:
C = zeros(size(A));
ub = unique(b);
for ii = 1:numel(ub)
C(:,ub(ii)) = sum(A(:,b == ub(ii)),2);
end
disp(C);
Another way:
[bg,gidx] = findgroups(b);
C = zeros(size(A));
C(:,gidx) = splitapply(@(x)sum(x,2),A,bg);
disp(C);
更多回答（1 个）
Vilém Frynta
2023-2-6
0 个投票
This looks like homework.
It seems like you know what kind of functions you should work with. I'd recommend to study the documention of these functions and try to think it out. Feel free to share your progress.
If you are beginning with Matlab, it's good idea just to try (and learn from mistakes and experiments).
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