Asked by Piment
on 8 Apr 2013

I have a n elements vector a1 a2 ... an

and n same-sized matrices b1 b2 ... bn

how can I do a1*b1 + a2*b2 + ... + an*bn without loop? I was thinking if there's a way to do something like multidimentsional array dotwise multiplication? Thanks.

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Answer by per isakson
on 8 Apr 2013

Try

a * transpose( b )

where

a = [ a1, a2, ... an ] b = [ b1, b2, ... bn ]

Piment
on 13 Apr 2013

I'm not sure if I have made it clear enough, the thing is it's not gonna work because I've tried this before. this is what I did and what matlab spitted out:

>> a = [rand(1), rand(1), rand(1), rand(1)];

>> [b1, b2, b3, b4] = deal(magic(3));

>> b = [b1, b2, b3, b4];

>> a * transpose(b);

Error using *

Inner matrix dimensions must agree.

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