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MathGroup Archive 1999

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Re: HELP: Plot[]ing composite functions

  • To: mathgroup at
  • Subject: [mg16007] Re: HELP: Plot[]ing composite functions
  • From: Paul Abbott <paul at>
  • Date: Sat, 20 Feb 1999 02:52:01 -0500
  • Organization: University of Western Australia
  • References: <7ag4kt$>
  • Sender: owner-wri-mathgroup at

Alexander Sirotkin wrote:

> Simple question - after definition of a functions
> which looks like this "H[w] == Log[10, 1 + Exp[I2Pi w]]"
> I try to Plot[] it and get the "... not machine size real
> number at ..." error. 

Because you are trying to plot a complex-valued function.  Try

	H[w_] = Log[10, 1 + E^(I*2*Pi*w)]; 
	Plot[Abs[H[w]], {w, 0, 4}]; 

or, more efficiently,

	Plot[Evaluate[Abs[H[w]]], {w, 0, 4}]; 


Paul Abbott                                   Phone: +61-8-9380-2734
Department of Physics                           Fax: +61-8-9380-1014
The University of Western Australia           
Nedlands WA  6907                     mailto:paul at 

            God IS a weakly left-handed dice player

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