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 >