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MathGroup Archive 1996

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  • To: mathgroup at
  • Subject: [mg5384] Abs[]
  • From: Rob Peterson <robpeterson at>
  • Date: Thu, 5 Dec 1996 14:50:22 -0500
  • Organization: Sprint Internet Passport
  • Sender: owner-wri-mathgroup at

I may not understand the limitations of Abs[].

This works just fine:
s[L_]=I/(L+1/L);(* a complex function *)
(*The Abs[] of a complex function, which is real, apparently has a real
derivative and it is plotted.*)

However, If I put another "I" in the function definition, the derivative
of the Abs[] appears to have an imaginary component:
s[L_]=I/(L+I/L);(* has I instead of 1 *)

The error message is as follows
Plot::"plnr": (1 - I/L^2)* REAL "is not a mach. size real number".  For
some reason a factor of (1-I/L^2) showed up (REAL is some real

Can anyone give me a clue how I might be able to plot the derivative of
the Abs[] of this type of complex function?

I can't think of anything interesting to put here.

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