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Piment
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Vector and matrices dotwise multiplication

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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1 Answer

Answer by per isakson
on 8 Apr 2013

Try
a * transpose( b )
where
a = [ a1, a2, ... an ]
b = [ b1, b2, ... bn ]

  1 Comment

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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