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Re: Dot or Inner ... but not quite


On Jul 31, 2007, at 6:13 AM, Diamond, Mark wrote:

> I have two equi-length lists, the first of number, the second of
> (equi-length) lists of numbers , such as
>
> l1={1,4,3};
> l2={{1,7},{1,9},{5,2}};
>
> I want to produce 1*{1,7}+4*{1,9}+3*{5,2}
>
> It looks so close to Inner that I thought I could use it in some  
> form, but I
> have ended up using
>
> (#[[1]]*#[[2]])& /@ Transpose[{l1,l2}]
>
> Is there a better way using one of the builtin functions with which  
> I am
> unfamiliar?

You could just write what you want explicitly:

Plus@@(l1 l2)

or use Inner:

Inner[Times,l1,l2,Plus]

Regards,

Ssezi


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