RE: Plots with Variable Limits?

*To*: mathgroup at smc.vnet.net*Subject*: [mg24120] RE: [mg24100] Plots with Variable Limits?*From*: Wolf Hartmut <hwolf at debis.com>*Date*: Wed, 28 Jun 2000 02:11:42 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

> -----Original Message----- > From: A. E. Siegman [SMTP:siegman at stanford.edu] To: mathgroup at smc.vnet.net > Sent: Tuesday, June 27, 2000 6:52 AM > To: mathgroup at smc.vnet.net > Subject: [mg24100] Plots with Variable Limits? > > I want to make a test plot of a function f[x,a] versus x for some > trial value of the parameter a without fixing that parameter for > subsequent cells, e.g. something like > > Plot[ f[r,a], {x,-2a,2a} ] /. a->10 > > If I try this, Mathematica gives me a "Plot::plln" error -- but then > goes ahead and makes the correct plot anyway. > > I can of course turn off the error -- but what's a better, but still > clean and simple, way to accomplish this. > > Thanks siegman at stanford.edu > [Wolf Hartmut] You just need to wrap Plot with Unevaluated. Unevaluated[Plot[ f[r,a], {x,-2a,2a} ]] /. a->10 This prevents the evaluation of plot _before_ substitution occurs (which doesn't work and therefore generates the error message; after the error the original input was returned which then was replaced and evaluated correctly). Kind regards, Hartmut