Re: Extracting terms of a multivariate polynomial order by order

*To*: mathgroup at smc.vnet.net*Subject*: [mg80295] Re: Extracting terms of a multivariate polynomial order by order*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Thu, 16 Aug 2007 07:26:02 -0400 (EDT)*Organization*: Uni Leipzig*References*: <fa13t2$p5c$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, CoefficientArrays[Expand[(1 + x + y + z)^3], {x, y, z}] /. s_SparseArray :> Normal[s] may help you. Regards Jens Marcus P S wrote: > Hello, > > I have a multivariate polynomial (3 variables) from which I would > like to extract terms order by order. More explicitly, I want all the > lowest order terms, or all terms of the form > > c(L,M,N) x^L y^M z^N > > where L+M+N is smallest, and c(LMN) is some coefficient. If I have > this, I can extract order by order, and taylor to which order I want > to approximate my polynomial. > > I considered "Coefficients", but if I ask for the coefficients of > the form x^2 z^2, it may return something like "1 + y", which is not > what I want. Moreover, I have to explicitly request each possible > term of a given order, which seems too mechanical/repetitive to be the > "right way" to do things. The function for manipulating SeriesData > objects are similarly limited. > > I am assuming that there is function in Mathematica (even 5.2) that > will do this. Any suggestions would be greatly welcome. > > Thanks in advance. > > Marcus Silva > >