Re: Why are the functions different?
- To: mathgroup at smc.vnet.net
- Subject: [mg55636] Re: Why are the functions different?
- From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
- Date: Fri, 1 Apr 2005 05:36:08 -0500 (EST)
- Organization: Uni Leipzig
- References: <d2g5mg$f2m$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
you mean
f1[x_] = Normal[Series[Tanh[x], {x, 0, 5}]]
f0[x_] := x - x^3/3 + (2*x^5)/15
because if you call f1 with a numeric argument,say
x->1, you evaluate
Normal[Series[Tanh[1],{1,0,5}]
and this can not work. With you definition the
Series[] function
is executed in every call of f1[] and this waste
computation time.
Regards
Jens
"Helge Stenstroem"
<helge.stenstrom.NOSPAM at NOSPAMericsson.com>
schrieb im Newsbeitrag
news:d2g5mg$f2m$1 at smc.vnet.net...
> 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
>