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MathGroup Archive 1999

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  • To: mathgroup at
  • Subject: [mg18699] Re: POLE-ZERO PLOTS
  • From: Eckhard Hennig <hennig at>
  • Date: Sat, 17 Jul 1999 02:36:28 -0400
  • Organization: ITWM
  • References: <7mjsbi$>
  • Sender: owner-wri-mathgroup at

>In control systems, it is a custom to represent the poles of a transfer
>function by "X", and the zeros by "o".  When, I use mathematica to get the
>pole-zero plot, I am not sure how to display poles with crosses "x"...the
>only function I'm aware of is PointSize...but this function uses a
>Is there anybody out there who can propose a straightforward way to do it.

Instead of the graphics primitive Point, use the function CrossMark defined
below to mark the poles. The Graphics command gives you a rough idea how to
display a P/Z plot. However, unless you are determined to write your own P/Z
or root locus plot routine, you may also want to check out the evaluation
version of our circuits and systems analysis toolbox Analog Insydes. Its
graphics module includes a root locus plot function (see URL in my sig).

-- Eckhard

CrossMark[sz_][{x_, y_}] :=
  { Line[{Scaled[{-sz,  sz}, {x, y}], Scaled[{ sz, -sz}, {x, y}]}],
    Line[{Scaled[{-sz, -sz}, {x, y}], Scaled[{ sz,  sz}, {x, y}]}] }

Graphics[{CrossMark[0.02][{1,1}], CrossMark[0.05][{1.5,0.5}]},
    PlotRange->{{0,2},{0,2}}, Axes->True, AspectRatio->1]
  // Show

Dipl.-Ing. Eckhard Hennig      mailto:hennig at
Institut fuer Techno- und Wirtschaftsmathematik e.V. (ITWM)
Erwin-Schroedinger-Strasse,  67663 Kaiserslautern,  Germany
  Voice: +49-(0)631-205-3126    Fax: +49-(0)631-205-4139

     ITWM - Makers of Analog Insydes for Mathematica

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