Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2000
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2000

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: I do not understand

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25440] Re: I do not understand
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Sun, 1 Oct 2000 02:44:23 -0400 (EDT)
  • Organization: Universitaet Leipzig
  • References: <8r180o$hin@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

y'[t] is internal written as

Derivative[1][y][t] and this can't match a rule for y[t].
If you plan to replace derivatives you should use a construction like

y'[t] /. Thread[{#, D[#, t]} & /@ (y[t] -> ySer)]

In the fitst case

y[t] + y'[t] /. y[t]->ySer

only y[t] is replaced but Mathematica see a sum with
a series and expand y'[t] also to an series.

Regards
  Jens

Borut L wrote:
> 
> Hello,
> 
> ySer=Series[y[t],{t,0,3}]
> 
> If I apply this rule like this
> (y[t]+y'[t])/.y[t]->ySer
> both y[t] and y'[t] changes appropriately
> 
> If I apply
> y'[t]/.y[t]->ySer
> nothing happens
> 
> Why is that?


  • Prev by Date: Re: NDSolve : Stopping condition
  • Next by Date: Re: minimizing f(x,y) ???!!!!
  • Previous by thread: Re: NDSolve : Stopping condition
  • Next by thread: Re: I do not understand