Re: Possible Bug in ArcTan ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg64791] Re: [mg64770] Possible Bug in ArcTan ?*From*: Bruce Miller <brucem at wolfram.com>*Date*: Thu, 2 Mar 2006 19:28:28 -0500 (EST)*References*: <200603021148.GAA05303@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Mr. Denton, My experiments did not show anything odd. Could you post your code (InputForm) and version number? For example, In[1]:= $VersionNumber Out[1]= 5.2 In[7]:= dat = Table[{x,ArcTan[x]},{x,-2/100,2/100,0.005}]; ListPlot[dat]; Bruce Miller Technical Support Wolfram Research, Inc. support at wolfram.com http://support.wolfram.com/ 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!

**References**:**Possible Bug in ArcTan ?***From:*"JCDenton" <post4uw@web.de>