MathGroup Archive 2006

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Possible Bug in ArcTan ?

  • To: mathgroup at
  • Subject: [mg64791] Re: [mg64770] Possible Bug in ArcTan ?
  • From: Bruce Miller <brucem at>
  • Date: Thu, 2 Mar 2006 19:28:28 -0500 (EST)
  • References: <>
  • Sender: owner-wri-mathgroup at

Mr. Denton,

My experiments did not show anything odd.  Could you post your
code (InputForm) and version number?

For example,



dat = Table[{x,ArcTan[x]},{x,-2/100,2/100,0.005}];

Bruce Miller
Technical Support
Wolfram Research, Inc.
support at

On Mar 2, 2006, at 5:48 AM, JCDenton wrote:

> Hi Group!
> I am describing resonant electrical systems with Mathematica. So there
> is a lot of dealing with complex numbers and functions. One important
> function is:
> phi=ArcTan[Im/Re]
> This function is zero when Im = 0. The problem is, that when I plot
> this function it shows some strange behaviour near this zero point. It
> looks somehow, as if the function values are multiplied with -1 or
> something like that. I also tried to calculate a table an plot this
> with gnuplot where the stepsize was 0.005. I was the same strange
> situation. So I am sure it is not the Plot function that is buggy but
> the ArcTan itself. I also tried the table with step size 0.05 and I get
> the "right" picture with gnuplot. Is this a known bug? I have not found
> something about it yet.
> I realy need this function, since it is a very important operation in
> complex calculation.
> Thank you!

  • Prev by Date: Re: simplifying a summation / integral
  • Next by Date: Re: No mesh with Graphics3D
  • Previous by thread: Possible Bug in ArcTan ?
  • Next by thread: Re: Possible Bug in ArcTan ?