Re: Why are the functions different?
- To: mathgroup at smc.vnet.net
- Subject: [mg55635] Re: [mg55609] Why are the functions different?
- From: "Florian Jaccard" <florian.jaccard at he-arc.ch>
- Date: Fri, 1 Apr 2005 05:36:07 -0500 (EST)
- Reply-to: <florian.jaccard at he-arc.ch>
- Sender: owner-wri-mathgroup at wolfram.com
Hello Helge !
If you define f1[x_]:=... ,
and you plot : Plot[f1[x],{x,0,5}] ,
x is replaces by 0, 0+very small , etc. to calculate the points of the
ploting.
Mathematica will then try to find f1[0]=Normal[Series[Tanh[0],{0,0,5}]] ,
which is of course not possible!
You have 2 possibilities to do what you want :
1)
define : f1[x_]= Normal[Series[Tanh[x], {x, 0, 5}]]
2)
f1[x_]:=...
and : Plot[Evaluate[f1[x],{x,0,5}]]
Regards
F.Jaccard
-----Message d'origine-----
De : Helge Stenstroem [mailto:helge.stenstrom.NOSPAM at NOSPAMericsson.com]
Envoyé : jeu., 31. mars 2005 08:24
À : mathgroup at smc.vnet.net
Objet : [mg55609] Why are the functions different?
How are these two functions (f0 and f1) different? f0 can be plotted,
but f1 cannot.
f1[x_] := Normal[Series[Tanh[x], {x, 0, 5}]]
f0[x_] := x - x^3/3 + (2*x^5)/15
When evaluated like this:
f0[x]
f1[x]
they look the same.
The following gives error messages if f0 is replaced by f1.
Plot[{Tanh[z], f0[z]}, {z, -1, 1}]
(Mathematica 4.1 on Windows 2000)
--
Helge Stenström