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MathGroup Archive 1994

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Re: matrix of coefficients?

  • To: mathgroup at christensen.cybernetics.net
  • Subject: Re: matrix of coefficients?
  • From: Richard Mercer <richard at rmercer.wright.edu>
  • Date: Tue, 25 Oct 1994 08:29:08 -0400

>  Dear mathgroupers:
>  

>  If varsN = a list of N variables, and if exprsN = a list
>  of of N expressions, each one linear in the variables of
>  varsN,
>  

>  Is there some operator (that I haven't found yet), or
>  some clever way to use a nonobvious operator, to get the
>  matrix of coefficients?
>  

>   I'm doing it, but it is not a pretty sight.  I just have
>  a feeling there must be some neat way to do this very
>  commonly needed operation.  Thanks-  Martin McClain,
>  Chemistry, Wayne State University, Detroit
>  


I agree.
What you want is

Outer[Coefficient,exprsN,varsN]

In[11]:=
exprsN = {3x + 4y + 5z, 6x + 7y + 8z, 9x + 10y + 11z};
varsN = {x,y,z};
Outer[Coefficient,exprsN,varsN]
Out[13]=
{{3, 4, 5}, {6, 7, 8}, {9, 10, 11}}


Try it!


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