multiply element of a row vector (A) by corresponding row of matrix (B) and sum

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Isma
Isma 2015-9-3
评论： Matt J 2015-9-3
Hi
I am currently looking for an assistance on the way to perform such calculation:
A=[0 1 2 3];B=[1 2;3 4;5 6;7 8];
0*1 + 0*2
C= 1*3 + 1*4
2*5 + 2*6
3*7 + 3*8
==> C=[0;7;22;45]
I had a look at
bsxfun(@times,,)
but it can't be useful here (unfortunately).
Best,

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采纳的回答

Star Strider
Star Strider 2015-9-3
This works:
C = sum(bsxfun(@times, A', B),2);
To get bsxfun to work here, you have to transpose ‘A’ so that the two arguments have a dimension in common. Then sum across the columns (dimension 2).

更多回答（1 个）

Matt J
Matt J 2015-9-3
C=A(:).*sum(B,2);
  2 个评论
Matt J
Matt J 2015-9-3
I had a look at bsxfun(@times,,) but it can't be useful here (unfortunately).
It's actually fortunate that you can avoid bsxfun. If B is an M x N matrix, then using bsxfun will require M*N multiplications, whereas with what I propose, you only do M multiplications.

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