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Re: Working with D, definition of a function

• To: mathgroup at smc.vnet.net
• Subject: [mg75975] Re: Working with D, definition of a function
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Mon, 14 May 2007 03:42:59 -0400 (EDT)
• References: <f26nfr$450$1@smc.vnet.net>

Hi,

you mean

ComPath[w_, mu_, bias_] := mu*(\[ImaginaryI]*w + 1) 2 + bias;
ComPathPrime[w_, mu_] = D[ComPath[w, mu, 0], w]

notice the Set[] insead of your SetDelayed[]

Regards
   Jens


Thomas Schmelzer wrote:
> Hi,
> 
> I have defined a map
> 
> ComPath[w_, mu_, bias_] := mu*(\[ImaginaryI]*w + 1)^2 + bias;
> Now, I would like to use the derivative with respect to w as a further 
> function.
> 
> D[ComPath[w, mu, 0], w]
> 
> gives the answer I expect, but
> 
> ComPathPrime[w_, mu_] := D[ComPath[w, mu, 0], w];
> 
> doesn't seem to make sense
> 
> ComPathPrime[2, 1]
> 
> results in
> 
> General::ivar : 2 is  not a valid variable.
> 
> 
> 
> If it seems I have a lack of knowledge about the internals of Mathmatica - 
> that's right.
> 
> Can you briefly explain why this should not work?
> 
> Best,
> 
> Thomas
> 
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