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MathGroup Archive 2001

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Re: Expansion Coefficients in Multivariable Series Expansions?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg26595] Re: Expansion Coefficients in Multivariable Series Expansions?
  • From: "Ersek, Ted R" <ErsekTR at navair.navy.mil>
  • Date: Thu, 11 Jan 2001 10:39:09 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

A. E. Siegaman basically had a polynomial in several variables say (x,y,z)
and 
as I understand it wanted the coefficient of (x) as returned by the
following.

In[1]:=
  poly = 3x + Pi x - 2x y^2 + x z^3;
  Part[CoefficientList[poly,{x,y,z}],2,1,1]

Out[1]=
   3 + Pi

---------------
Then if poly is a polynomial in (w,u,v,x,y,z) you can get the coefficient of
x by using the following.

Part[ CoefficientList[poly, {w,u,v,x,y,z}],  1,1,1,,2,1,1]

---------------
Lookup CoefficientList on my website
http://www.verbeia.com/mathematica/tips/Tricks.html 
for a detailed explanation of this function.

---------------
Regards,
Ted Ersek



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