Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2004
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2004

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

Search the Archive

Problem with transformation rules in Plot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg48498] Problem with transformation rules in Plot
  • From: Alain Cochard <alain at geophysik.uni-muenchen.de>
  • Date: Wed, 2 Jun 2004 04:22:08 -0400 (EDT)
  • Reply-to: alain at geophysik.uni-muenchen.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hello.  I would be grateful if someone could explain to me the
following behavior (i.e., is it normal? why?), or point me to a
relevant part of a manual:

Mathematica 4.0 for Linux
Copyright 1988-1999 Wolfram Research, Inc.
 -- Motif graphics initialized -- 

In[1]:= f[x_]:=a x ; g[x_]:=2 a x ;

In[2]:= Plot[ f[x]/.{a->1} , {x,0,1}]  (* Fine *)

Out[2]= -Graphics-

In[3]:= {f[x],g[x]}/.{a->1} 

Out[3]= {x, 2 x}  (* Fine, just checking *)

In[4]:= Plot[{f[x],g[x]}/.{a->1} , {x,0,1}]

Plot::plnr: {f[x], g[x]} /. {a -> 1} is not a machine-size real number at x = 
              -8
    4.16667 10  .

Plot::plnr: {f[x], g[x]} /. {a -> 1} is not a machine-size real number at x = 
    0.040567.

Plot::plnr: {f[x], g[x]} /. {a -> 1} is not a machine-size real number at x = 
    0.0848088.

General::stop: Further output of Plot::plnr
     will be suppressed during this calculation.

Out[4]= -Graphics-

(* So the question is: why does it work for f[x] alone, and not for
f[x] and g[x]? *)

(* The following works fine, but is there a better workaround? *)

In[5]:= data={a->1} ; Plot[{ f[x]/.data , g[x]/.data }, {x,0,1}]


Many thanks in advance,
Alain Cochard




  • Prev by Date: Re: 3D fitting of data points
  • Next by Date: Symbolic use of numerical function FindRoot via ?NumericQ
  • Previous by thread: Re: 3D fitting of data points
  • Next by thread: Re: Problem with transformation rules in Plot