Re: Derivatives D[ ] as Functions inside Tables; Need Help!
- To: mathgroup at smc.vnet.net
- Subject: [mg13193] Re: [mg13102] Derivatives D[ ] as Functions inside Tables; Need Help!
- From: "Jrgen Tischer" <jtischer at col2.telecom.com.co>
- Date: Mon, 13 Jul 1998 07:42:42 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Hi Anthony,
I recommend you read first
2.4.8 Immediate and Delayed Definitions
in the Book. Then you will understand that you tried to calculate things
like
D[a Cos[0] + a^2 Sin[0],0]
(so the message General::ivar: 0 is not a valid variable).
Jrgen
-----Original Message-----
From: AES <siegman at ee.stanford.edu>
To: mathgroup at smc.vnet.net
Subject: [mg13193] [mg13102] Derivatives D[ ] as Functions inside Tables; Need
Help= !
>I'm trying to define a function f1[a,x] and its derivative f2[a,x],
>where from my point of view x is the independent variable and "a" is
>a parameter I'll change on different runs. So I write, as a simple
>example:
>
> Remove["Global`*"]
>
> f1[a_,x_] :=a Cos[x] + a^2 Sin[x]
>
> f1[a,x]
>
> f2[a_,x_] := D[f1[a,x],x]
>
> f2[a,x]
>
> a=2
>
> f1[a,x]
>
> f2[a,x]
>
> Table[{x, f1[a,x], f2[a.x]} // N, {x,0,4}] // TableForm
>
>and everything looks fine -- except the function f2[a,x] will not
>evaluate inside the Table[ ]. I don't understand this -- help in
>understanding will be much appreciated.
>
> siegman at ee.stanford.edu
>