Re: ParametricPlot problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg97811] Re: ParametricPlot problem*From*: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>*Date*: Sun, 22 Mar 2009 05:48:55 -0500 (EST)*References*: <gq2eri$ea1$1@smc.vnet.net>

Hi Jakub, Instead of f, you could try Exp[f]: ParametricPlot[{Re[transfer[Exp[f]]], Im[transfer[Exp[f]]]}, {f, 0, 10}, PlotRange -> All] You could treat the original plot for f in [0,1] separately (but it doesn't do much here). Cheers -- Sjoerd On Mar 21, 12:17 pm, "Serych Jakub" <Ser... at panska.cz> wrote: > Dear M users, > I'm trying to draw phasor characteristic of simple RC low pass filter. Its > transfer function is: > > r = 100; > c = 0.00001; > transfer[f_] := 1/(1 + I 2 \[Pi] f r c); > > The phasor characteristic should be drawn with: > > ParametricPlot[{Re[transfer[f]], Im[transfer[f]]}, {f, 0, Infinity}] > > I can understand, that Mathematica has problem with calculation of the > transfer function for frequency from 0 to Infinity, so I tried to use 10^ 8 in > the place of infinity. But as the ParametricPlot IMHO subdivides the > frequency range into constant intervals, it draws piece of the curve only > for frequencies near to 10^8. > I found that the relatively reasonable result is with frequency range 0 to > 10^3: > > ParametricPlot[{Re[transfer[f]], Im[transfer[f]]}, {f, 0, 10^3}] > > but there is missing the part of curve near to coordinates origin. > > Is there any way to tell the ParametricPlot to divide the interval of the > frequency in logarithmic manner to have the possibility to draw the phasor > characteristic in the bigger frequency range? > > I tried the PlotPoints and PerformanceGoal options, but it doesn't help (or I > cannot use it). > > Thanks a lot for any help > > Jakub