Re: Re: Re: how fill PolarPlot?

• To: mathgroup at smc.vnet.net
• Subject: [mg84463] Re: [mg84455] Re: [mg84431] Re: [mg84420] how fill PolarPlot?
• From: Brett Champion <brettc at wolfram.com>
• Date: Wed, 26 Dec 2007 05:08:04 -0500 (EST)
• References: <20071224091350.HNWYO.62626.root@eastrmwml30> <200712251128.GAA18408@smc.vnet.net>

```On Dec 25, 2007, at 5:28 AM , Murray Eisenberg wrote:

> Your response suggests that perhaps it's not possible directly to use
> polar coordinates themselves as arguments to the ColorFunction
> function.
>
> If so, that's a shame.
>

From the PolarPlot documentation:

"The arguments supplied to functions in  MeshFunctions and
RegionFunction are  x, y, \[Theta], r. Functions in  ColorFunction
are by default supplied with scaled versions of these arguments. "

You can find examples under PolarPlot > Examples > Options >
ColorFunction.

Brett Champion
Wolfram Research

> Bob Hanlon wrote:
>> PolarPlot[Cos[2 theta], {theta, 0, 2 Pi},
>>  ColorFunction ->
>>   Function[{x, y}, If[-Pi/4 <= ArcTan[x, y] <= Pi/4, Red, Blue]],
>>  ColorFunctionScaling -> False]
>>
>>
>> Bob Hanlon
>>
>> ---- Murray Eisenberg <murray at math.umass.edu> wrote:
>>> I was finally able to do this with Epilog->{Inset[RegionPlot[...]]}.
>>>
>>> Below is the entire code for the embellished plot I wanted.  I am
>>> still
>>> unhappy with at the amount of work I had to do in order to adjust
>>> the
>>> ImageSize of the filled leaf and the thickness of its boundary so
>>> as to
>>> cover up the underlying blue boundary of that leaf from the
>>> PolarPlot.
>>>
>>> Some of that adjustment could probably be avoided by using a
>>> ColorFunction for the overall POlarPlot.  But how does one set up
>>> ColorFunction for PolarPlot so as to specify using, say, one
>>> color for
>>> part of the plot and another for another part, depending on the
>>> value of
>>> theta alone?
>>>
>>> I found no example of ColorFunction in the documentation.  I
>>> tried, e.g.,
>>>
>>>   PolarPlot[Cos[2 theta], {theta, 0, 2 Pi},
>>>     ColorFunction ->
>>>       Function[{theta,r}, If[-Pi/4 <= theta <= Pi/4, Red, Black]]]
>>>
>>> but that doesn't work as expected.
>>>
>>> The finished figure's code:
>>>
>>>    txt[t_,{x_,y_}]:=Style[Text[t,{x,y}],FontSize->30,FontWeight-
>>> >Bold]
>>>    {xmin,xmax}={-1.425,1.425}; {ymin,ymax}={-1.25,1.25};
>>>
>>>    PolarPlot[Cos[2t],{t,0,2Pi}, PlotRange->{{xmin,xmax},
>>> {ymin,ymax}},
>>>      PlotStyle->{ColorData["Legacy","SteelBlue"], Thickness[0.007]},
>>>      Ticks->None,
>>>
>>>      Epilog->{
>>>        Inset[RegionPlot[(x^2+y^2)^(3/2)<=x^2-y^2,{x,-0.02,1},
>>> {y,-1,1},
>>>                PlotStyle->ColorData["HTML","Gold"],
>>>                BoundaryStyle->Directive[Thickness[0.025],
>>>                Frame->False,AspectRatio->Automatic,
>>>                ImageSize->2.6*72],
>>>           {0.5,0}],
>>>         Black,Thick,Dashing[{0.045,0.03}],
>>>         Line[{{0,0},{0.85,0.85}}],Line[{{0,0},{0.85,-0.85}}],
>>>         Dashing[{}],Thick,
>>>         Arrow[{{xmin,0},{xmax,0}}],Arrow[{{0,ymin},{0,ymax}}],
>>>      },
>>>    ImageSize->7*72]
>>>
>>> Murray Eisenberg wrote:
>>>> I Mathematica 6 I have a PolarPlot, e.g., a 4-leaved rose:
>>>>
>>>>    PolarPlot[Cos[2 theta], {theta, 0, 2 Pi}]
>>>>
>>>> How can I fill the inside -- or, what I really want, just the
>>>> leaf in
>>>> the right half-plane -- with some color?
>>>>
>>>> I note that Filling does not seem to be an option for PolarPlot
>>>> (or for
>>>> what would be almost as good, ParametricPlot).
>>>>
>>>> I tried including the following (obtained by converting from :
>>>>
>>>>    Prolog->RegionPlot[(x^2 + y^2)^(3/2) <= x^2-y^2, {x,-0.02,1},
>>>> {y,-1,1},
>>>>        Frame->False, AspectRatio->Automatic]
>>>>
>>>> However, that led to a mysterious error message:
>>>>
>>>>    \$Aborted is not a Graphics primitive or directive.
>>>>
>>>> (Perhaps because of an incompatibility of a Prolog with cartesian
>>>> coordinates inside a polar coordinate plot??)
>>>>
>>> --
>>> Murray Eisenberg                     murray at math.umass.edu
>>> Mathematics & Statistics Dept.
>>> Lederle Graduate Research Tower      phone 413 549-1020 (H)
>>> University of Massachusetts                413 545-2859 (W)
>>> 710 North Pleasant Street            fax   413 545-1801
>>> Amherst, MA 01003-9305
>>>
>>
>
> --
> Murray Eisenberg                     murray at math.umass.edu
> Mathematics & Statistics Dept.
> Lederle Graduate Research Tower      phone 413 549-1020 (H)
> University of Massachusetts                413 545-2859 (W)
> 710 North Pleasant Street            fax   413 545-1801
> Amherst, MA 01003-9305

```

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