Re: VectorPlot on a Circle

• To: mathgroup at smc.vnet.net
• Subject: [mg114801] Re: VectorPlot on a Circle
• From: Helen Read <readhpr at gmail.com>
• Date: Fri, 17 Dec 2010 03:30:49 -0500 (EST)
• References: <ie297c\$mrj\$1@smc.vnet.net> <201012130852.DAA09458@smc.vnet.net> <iecqvv\$bld\$1@smc.vnet.net>

```On 12/16/2010 5:51 AM, Dave Snead wrote:
> Hi,
>
> I'm trying to do a vector plot but confine the vectors to a unit circle.
>
> VectorPlot[
> If[Abs[x^2 + y^2 - 1] == 0, {x, y}, {0, 0}], {x, -1, 1}, {y, -1, 1}]
> only plots a couple of vectors, not the dense set of vectors that I want.
>
> and
> VectorPlot[
> If[Abs[x^2 + y^2 - 1]<.1, {x, y}, {0, 0}], {x, -1, 1}, {y, -1, 1}]
> plots lots of vectors but they're on an annulus rather than a circle.

You could specify exactly what points to use.

points = Table[{Cos[t], Sin[t]}, {t, 0, 2 \[Pi], \[Pi]/24}];

VectorPlot[{x, y}, {x, -1, 1}, {y, -1, 1}, VectorPoints -> points]

--
Helen Read
University of Vermont

```

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