How to make up the diagonal summation without for loop and with the fastest way!

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HYUNCHUL
HYUNCHUL 2014-4-1
评论： Andrei Bobrov 2014-4-1
A =
1 7 13
2 8 14
3 9 15
4 10 16
5 11 17
6 12 18
B =
1, (2+7), (3+8+13), (4+9+14), (5+10+15) ... (12+17), 18
How to make the B vector?
Vector-wise would be good to perform the enhancement of computational time?

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采纳的回答

Andrei Bobrov
Andrei Bobrov 2014-4-1
A =[ 1 7 13
2 8 14
3 9 15
4 10 16
5 11 17
6 12 18];
B = sum(spdiags(rot90(A)));

更多回答（3 个）

Azzi Abdelmalek
Azzi Abdelmalek 2014-4-1
编辑：Azzi Abdelmalek 2014-4-1
A =[ 1 7 13
2 8 14
3 9 15
4 10 16
5 11 17
6 12 18]
[n,m]=size(A);
B=fliplr(A);
out=zeros(1,m+n-1);
for k=-n+1:m-1
out(k+n)=sum(diag(B,k));
end
out=fliplr(out)
Mischa Kim
Mischa Kim 2014-4-1
编辑：Mischa Kim 2014-4-1
Hyunchul, something like
fA = fliplr(A);
B = fliplr(arrayfun(@(i) sum(diag(fA,i)),-length(A(:,1))+1:length(A(1,:))-1));
Sean de Wolski
Sean de Wolski 2014-4-1
And just for fun (requires Image Processing):
B = zeros(size(A));
B(1) = 1;
B2 = bwdist(B,'cityblock')+1;
v = accumarray(B2(:),A(:))
Use Azzi's solution.

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