Re: How to select terms wanted in a series
- To: mathgroup at smc.vnet.net
- Subject: [mg85960] Re: How to select terms wanted in a series
- From: Grischika at mail.ru
- Date: Thu, 28 Feb 2008 03:00:58 -0500 (EST)
- References: <firstname.lastname@example.org>
On 27 =C6=C5=D7, 11:46, Barrow <GRsemi... at gmail.com> wrote: > Dear all, > > I have an expression, which is a sum of large number of terms, e.g. > > expression = x + 2x*y - x*y*z + u*x*y + 3u^2 > > And I want to select out terms with the factor (x*y). e.g. > > The terms in "expression" that I want are 2x*y, -x*y*z, u*x*y > > My first step is, > > allterms = Apply[List, expression] > > Then, I don't know how to extract the terms I want, I use > > Select[allterms, (# == x*y*_)&] > > But It doesn't work. > > Anyone has some good ideas? any help will be appreciated much! > Sincerely =9ABarrow There are many ways to do this. I prefer the next one: Apply[List,Expand[Coefficient[e1, x*y]*x*y]].