Re: Expansion Coefficients in Multivariate Series Expansions?

*To*: mathgroup at smc.vnet.net*Subject*: [mg26603] Re: [mg26579] Expansion Coefficients in Multivariate Series Expansions?*From*: Tomas Garza <tgarza01 at prodigy.net.mx>*Date*: Thu, 11 Jan 2001 10:39:13 -0500 (EST)*References*: <200101090651.BAA00200@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

I don't see why Coefficient[] doesn't work? In[1]:= d = (a*x + b*y + c*z)^5 Out[1]= (a*x + b*y + c*z)^5 In[2]:= Coefficient[d, x^2*y^2*z] Out[2]= 30*a^2*b^2*c In[3]:= Coefficient[d, x*y*z^3] Out[3]= 20*a*b*c^3 In[4]:= Coefficient[d, x*y^3*z] Out[4]= 20*a*b^3*c Unless, of course, I didn't quite get your question. Tomas Garza Mexico City ----- Original Message ----- From: "A. E. Siegman" <siegman at stanford.edu> To: mathgroup at smc.vnet.net Subject: [mg26603] [mg26579] Expansion Coefficients in Multivariate Series Expansions? > Given an expression that is the sum of products of integer powers of > three variables (say x,y,z) multiplied by numerical coefficients: > > f = c000 + c100 x + c010 y + c001 z + c110 x y + c211 x^2 y z + . . . > > where the cijk's are all real numbers, and f may or may not be in > Normal (or other) form, how do I find the coefficient of a particular > term, e.g. c100 for the x term (*not* c1000 + c110 y), or ckmn for the > x^k y^m z^n term? > > Neither Coefficient nor SeriesCoefficient seems to do this -- and the > SeriesCoefficient[expr, {n1,n2,n3,..}] syntax seems to be mentioned but > neither explained or illustrated in the on-line Help. > > Thanks, siegman at stanford.edu >

**References**:**Expansion Coefficients in Multivariate Series Expansions?***From:*"A. E. Siegman" <siegman@stanford.edu>