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Re: Plot difficulties <Error Machine Sized Real Number>

  • To: mathgroup at
  • Subject: [mg57998] Re: [mg57974] Plot difficulties <Error Machine Sized Real Number>
  • From: "David Park" <djmp at>
  • Date: Thu, 16 Jun 2005 05:35:55 -0400 (EDT)
  • Sender: owner-wri-mathgroup at


It is just what it says. Your function is not real over the plot domain.
(One has to wonder why your plot domain involves such small numbers.) You
can only plot real values so you have to investigate your function, maybe
exploring it with Table, and decide what is is you really want to plot. If
your function is truly a complex function then maybe you want to us Re and
Im  to plot the real and imaginary parts, or Abs to plot the absolute value.

David Park
djmp at

From: Eric [mailto:edcurtis at]
To: mathgroup at


I have a question regarding Plot.  Here is a snip of my code:

Plot[function1, {EE,0 ,2.9*1.6 10^-19}, PlotLabel->"function1"];
Plot:: plnr : function1 is not a machine-sized real number at EE =

function1 evalutates to 0. + 0.00195313i at this point.  In fact, at every
point the plot command gives an error the evaluation is completly imaginary.

Function1 is composed as follows:

Sqrt[1/(k1 Rc)] Sqrt[1/(k2i Rs)] (k2i m1 Rc Cos[k2i (Rc - Rs)] Sin[k1 Rc] -
(k1 m2 Rc Cos[k1 Rc] + (m1 - m2) Sin[k1 Rc]) Sin[k2i (Rc - Rs)])/ (m1
(Sqrt[1/(k2i Rc)] * Sqrt[k1  Rc]  Sqrt[k2i  Rc]  Sqrt[k2i Rs])

Where k2i is completely imaginary, m1>m2, and Rs>Rc

Any Suggestions?


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