add elements in a matrix

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sasso samer
sasso samer 2016-4-11
编辑： Azzi Abdelmalek 2016-4-12
I have a matrix like this
1 2 3 3 1 2 2 1 3
3 2 1 1 3 2 2 3 1
What i want to do is a 3x9 matrix that contains this
cell (1,1) . (1 + 3 + 2) - 1 .... 1(the first element) + 3(the fourth element) + 2(the 7th element) - 1(my initial cell)
cell (1,2) . (2 + 1 + 1) - 2 .... 2(the second element) + 1(the fifth element) + 1(the 8th element) - 2(my initial cell)
and so on... cell (1,5) . (1 + 2 + 1)-1 .... 1(the 5th element) + 2(2nd element) + 1(8th element) - 1(initial cell)
It's like calculating the total of all the numbers where the indices are separated by 3
output =
5 2 5 3 3 6 4 3 5
3 6 3 5 5 2 4 5 3
I have this code
for k1 = 1:2
for k2 = 1:3
S(k1,k2) = sum(a(k1,3+k2:3:end),2);
end
end
but it adds the first 3 number only, i want it to continue till the end of the matrix

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回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2016-4-11
编辑：Azzi Abdelmalek 2016-4-12
A=[1 2 3 3 1 2 2 1 3;3 2 1 1 3 2 2 3 1];
ff=numel(A(1,1:3:end))-1;
[n,m]=size(A);
[ii,jj]=ndgrid(1:n,1:m);
AA=[A A];
out=arrayfun(@(x,y) sum(AA(x,y+3:3:y+ff*3)),ii,jj)

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