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Working with D, definition of a function

• To: mathgroup at smc.vnet.net
• Subject: [mg75912] Working with D, definition of a function
• From: "Thomas Schmelzer" <thomas.??? at balliol.ox.ac.uk>
• Date: Sun, 13 May 2007 05:46:53 -0400 (EDT)
• Organization: Balliol College
• Reply-to: "Thomas Schmelzer" <thomas.??? at balliol.ox.ac.uk>

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