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MathGroup Archive 2007

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Re: Dot or Inner ... but not quite

  • To: mathgroup at smc.vnet.net
  • Subject: [mg79639] Re: Dot or Inner ... but not quite
  • From: "Mariusz Jankowski" <mjankowski at usm.maine.edu>
  • Date: Wed, 1 Aug 2007 04:53:21 -0400 (EDT)
  • Organization: University of Southern Maine
  • References: <f8n2rc$lp9$1@smc.vnet.net>

Mark, the Dot product does give the result you want, 

In[3]:= l1.l2

Out[3]= {20, 49}



Mariusz






>>> On 7/31/2007 at 6:27 AM, in message <f8n2rc$lp9$1 at smc.vnet.net>,
Diamond,
Mark<dot at dot.dot> 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?
> 
> Cheers,
> 
> Mark Diamond 


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