Re: Replace in operators
- To: mathgroup at smc.vnet.net
- Subject: [mg102902] Re: [mg102869] Replace in operators
- From: Patrick Scheibe <pscheibe at trm.uni-leipzig.de>
- Date: Wed, 2 Sep 2009 04:00:08 -0400 (EDT)
- References: <200909010750.DAA18607@smc.vnet.net>
Hi, the problem is, that your expression is evaluated to Plus[f[x],Derivative[1][f][x]] so what about ReleaseHold[Hold[f[x] + D[f[x], x]] /. f[x] :> g[x]] ? Cheers Patrick On Tue, 2009-09-01 at 03:50 -0400, did 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. >
- References:
- Replace in operators
- From: did <didier.oslo@hotmail.com>
- Replace in operators