Re: Re: Using Coefficient on an equation
- To: mathgroup at smc.vnet.net
- Subject: [mg95548] Re: [mg95515] Re: Using Coefficient on an equation
- From: DrMajorBob <btreat1 at austin.rr.com>
- Date: Wed, 21 Jan 2009 06:46:46 -0500 (EST)
- References: <200901181033.FAA13999@smc.vnet.net> <gl1bjo$93s$1@smc.vnet.net>
- Reply-to: drmajorbob at longhorns.com
In my Init file, I have the following code: Unprotect[Equal]; listableQ[f_]:=MemberQ[Attributes[f],Listable] Equal /: lhs : (f_Symbol)?listableQ[___, _Equal, ___] := Thread[Unevaluated[lhs], Equal] It causes Listable functions (like Coefficient) to thread over Equal. (I think that's useful.) Bobby On Tue, 20 Jan 2009 04:49:30 -0600, dh <dh at metrohm.com> wrote: > > > Hi, > > the first example is wrong. "Coefficient" only works on polynomial or > > list of polynomials. It does not work on expressions with head "Equal". > > Daniel > > > > DrMajorBob wrote: > >> f = a*x^2 + b*x + c == 0; > >> First@Coefficient[f, x^2] > >> > >> a > >> > >> or > >> > >> Coefficient[First@f, x^2] > >> > >> a > >> > >> Bobby > >> > >> On Sun, 18 Jan 2009 04:33:11 -0600, <carlos at colorado.edu> wrote: > >> > >>> If f=a*x^2+b*x+c, Coefficient[f,x^2] obviously returns a. > >>> But if f=a*x^2+b*x+c==0, it returns 0. > >>> > >>> The problem arose using the Calculus`VariationalMethods` package. > >>> It (unfortunately) returns the Euler-Lagrange equations as > >>> such, so I have to remove the useless ==0 appendage for > >>> Coefficient to work properly. Is there a simple direct way out? > >>> > >> > >> > >> > > > -- DrMajorBob at longhorns.com
- References:
- Using Coefficient on an equation
- From: carlos@colorado.edu
- Using Coefficient on an equation