Re: assigning functions
- To: mathgroup at smc.vnet.net
- Subject: [mg56232] Re: [mg56204] assigning functions
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Wed, 20 Apr 2005 05:30:04 -0400 (EDT)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
You don't need to define a separate function just use f'[x]
f[x_]:=x^2;
{f'[x],f'[2]}
{2 x,4}
Nonetheless, you can use Set ( = )
Clear[fprime];
fprime[x_]=D[f[x],x];
{fprime[x],fprime[2]}
{2 x,4}
or Evaluate the RHS of the SetDelayed ( := )
Clear[fprime];
fprime[x_]:=Evaluate[D[f[x],x]];
{fprime[x],fprime[2]}
{2 x,4}
Bob Hanlon
>
> From: juejung <juejung at indiana.edu>
To: mathgroup at smc.vnet.net
> Date: 2005/04/19 Tue AM 04:55:01 EDT
> To: mathgroup at smc.vnet.net
> Subject: [mg56232] [mg56204] assigning functions
>
> dear all,
>
> i would like to do the following.
> assign a function:
> f[x_] := x^2;
>
> take its derivate:
> D[f[x], x]
>
> and assign the result of this to a new function, like fprime[x]:
> fprime[x_] := D[f[x], x]
>
> unfortunately that doesn't work.
> when i try to evaluate fprime[2] i get an error message.
>
> can somebody please help, this haunts me for a while now.
>
> thanks and all the best
>
> juergen
>
>