Re: [Newbie] Interpreting output
- To: mathgroup at smc.vnet.net
- Subject: [mg56657] Re: [Newbie] Interpreting output
- From: David Bailey <dave at Remove_Thisdbailey.co.uk>
- Date: Mon, 2 May 2005 01:32:39 -0400 (EDT)
- References: <d51nl8$cu9$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
You really can't expect to take the derivative of a function defined by
an arbitrary definition like that! D is meant to be used on algebraic
expressions. However, you can define functions using Piecewise to do
what you want. For example:
f[x_,c_]=Piecewise[{{x,x<c},{x-1,x\[GreaterEqual]c}}]
D[f[x,c],x]//FullSimplify
1
Having said that, I rather think that answer should contain a Dirac
delta function to cover the discontinuity at x=c!
David Bailey
dbaileyconsultancy.co.uk