Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2008

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Extracting free parameters from a Solve result

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93932] Re: Extracting free parameters from a Solve result
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Fri, 28 Nov 2008 07:12:13 -0500 (EST)
  • Organization: Uni Leipzig
  • References: <ggog1b$s65$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

expr = {{W11 -> W44, W12 -> -W34, W13 -> W34, W14 -> -W23 - W33 + W44,
     W22 -> W33, W24 -> -W34}};

Union[Cases[expr /. (_ -> a_) :> a, _Symbol, Infinity]]

??

Regards
   Jens

carlos at colorado.edu wrote:
> In solving a Sylvester matrix equation, Solve is given
> 18 equations in 10 variables: v= {W11,W12,W13,W14,W22,
> W23,W24,W33,W34,W44}  It returns
> 
>  {{W11->W44, W12->-W34, W13->W34,
>   W14->-W23-W33+W44, W22->W33, W24->-W34}}
> 
> How do I extract the 4 variables: W44,W34,W23,W33 left
> over on the right of the ->, and place them in an ordered list:
> 
> pars={W23,W33,W34,W44}
> 
> I guess the simplest way would be to Drop the dependent
> variables from the v list but the details escape me.  Thanks.
> 


  • Prev by Date: Comment display style?
  • Next by Date: Re: v.7.0 issues
  • Previous by thread: Extracting free parameters from a Solve result
  • Next by thread: Re: Extracting free parameters from a Solve result