MathGroup Archive 2009

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

Search the Archive

Re: Replace in operators

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102935] Re: [mg102869] Replace in operators
  • From: "Elton Kurt TeKolste" <tekolste at fastmail.us>
  • Date: Wed, 2 Sep 2009 04:06:03 -0400 (EDT)
  • References: <200909010750.DAA18607@smc.vnet.net>

I think you can get all of the derivatives of f and preserve all of the
arguments with 

expression /. {f[x] -> g[x], 
  Derivative[n_][f][z_] -> Derivative[n][g][z]

drekt

On Tue, 01 Sep 2009 03:50 -0400, "did" <didier.oslo at hotmail.com> wrote:
> I can't figure out how to force Mathematica to replace
> f[x] by g[x] in expressions involving operators.
> For example:
> 
> f[x] + D[f[x],x] /. f[x] -> g[x]
> 
> f is not replaced in the derivative. I found
> somewhere in the manual that the replacement
> does not work on operators, but then it does
> not indicate how to do it.
> 
> In my real problem, f[x]->g[x] is a (long)
> list of complicated transformations resulting
> from the resolution of many equations.
> Thus, changing f[x]->g[x] by f->g is not
> an option.
> 
> f[x] + D[f[x],x] is actually a complicated
> expression involving many operators.
> 
> There are no ways I can do the
> substitution by hand, bit by bit.
> 
> Any suggestions ?
> Thanks
> 
> PS: it may help to precise the context.
> I'm trying to solve a system of PDEs by
> a small parameter expansion. Solving the
> system at order N, I want to re-inject the
> results into the equations at order N+1.
> 
Regards,
Kurt Tekolste



  • Prev by Date: Re: Nesting functional commands
  • Next by Date: Re: Faster alternative to AppendTo?
  • Previous by thread: Re: Replace in operators
  • Next by thread: Re: Replace in operators