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2.5 Graphics 89
means of the PlotPoints option. The poles and zeros of the transfer function are displayed as red
crosses and green circles, respectively.
In[13]:= RootLocusPlot[H4[s, a], {a, 3, 5}]
a = 3.000e0 .. 5.000e0 (0% .. 100%)
2.0E0
Im s
Poles
0%
-2.0E0 -1. -0.5
1.
-1.
Re s
100%
Zeros
0%
-2.0E0
100%
Out[13]= Graphics
RootLocusPlot Options
RootLocusPlot inherits its options from Graphics and adds its own options like PoleStyle and
ZeroStyle to Options[RootLocusPlot]. With these options you can customize the display of poles
and zeros, e.g. for better black-and-white printouts. The syntax of the PoleStyle option is
PoleStyle −> mark[size, colorfunc, grstyle]
where mark specifies the marker symbol (e.g. CrossMark, PlusMark, CircleMark, SquareMark, and
PointMark), size denotes the size of the marker in scaled coordinates, colorfunc is a pure function that
returns a color value for an argument between and , and grstyle is a Mathematica graphics style
or a sequence of styles, such as Hue or Thickness. Note that everything mentioned above applies
to the ZeroStyle option as well.
In the following command line we instruct RootLocusPlot to modify the styles for the pole and
zero markers: