Re: VectorPlot on a Circle

*To*: mathgroup at smc.vnet.net*Subject*: [mg114781] Re: VectorPlot on a Circle*From*: "Dave Snead" <dsnead6 at charter.net>*Date*: Fri, 17 Dec 2010 03:27:11 -0500 (EST)*References*: <ie297c$mrj$1@smc.vnet.net> <201012130852.DAA09458@smc.vnet.net> <201012161049.FAA11856@smc.vnet.net> <086FCBD6-0907-4B16-8A41-48E4A8258A16@trm.uni-leipzig.de> <2E8ED7A7B0E645D5A110089B1ED87107@DV73080US> <C3A25BE7-34C3-4778-B0BC-955567831DA0@trm.uni-leipzig.de>

Patrick, Your solution, VectorPlot[{x, y}, {x, -2, 2}, {y, -2, 2}, VectorPoints -> Table[{Cos[phi], Sin[phi]}, {phi, 0, 2 Pi, 0.1}]] works great! Thanks, Dave -----Original Message----- From: Patrick Scheibe Sent: Thursday, December 16, 2010 10:46 AM To: Dave Snead Cc: Mathematica Group Subject: [mg114781] Re: [mg114766] VectorPlot on a Circle Ahh, ok I have read you mail too fast. Usually (in the case of other plots too) this is no easy to achieve since the plot samples in any way your domain. Your line on the circle is infinite small and the sampling does not find such things easily. Nevertheless, in your case and in your *real* application too, you may can use something like VectorPlot[{x, y}, {x, -2, 2}, {y, -2, 2}, VectorPoints -> Table[{Cos[phi], Sin[phi]}, {phi, 0, 2 Pi, 0.1}]] Hope this helps, Cheers Patrick On Dec 16, 2010, at 7:20 PM, Dave Snead wrote: > Hi Patrick, > > Thanks, but > VectorPlot[{x, y}, {x, -1, 1}, {y, -1, 1}, > RegionFunction -> Function[{x, y}, x^2 + y^2 < 1]] > plots vectors on the unit disk, I just want to define the vectors on the > unit circle. > > What I would like is something like > VectorPlot[{x, y}, {x, -1, 1}, {y, -1, 1}, > RegionFunction -> Function[{x, y}, x^2 + y^2 == 1]] > but this function only does a sparse plot of the vectors, and some > of them are not on the circle! > > I'd like to know if Mathematica has the capability to restrict these > vectors to a one dimensional, > rather than a two dimensional region and do a decent plot. > > Cheers, > Dave > > -----Original Message----- From: Patrick Scheibe > Sent: Thursday, December 16, 2010 5:08 AM > To: Dave Snead > Cc: mathgroup at smc.vnet.net > Subject: Re: [mg114766] VectorPlot on a Circle > > Hi, > > what about > > VectorPlot[{x, y}, {x, -1, 1}, {y, -1, 1}, > RegionFunction -> Function[{x, y}, x^2 + y^2 < 1]] > > ? > > Cheers > Patrick > > > On Dec 16, 2010, at 11:49 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. >> >> Is there any way to do this? >> >> Or more generally is there any way to confine the vectors to a curve. >> Or, kicking the dimension up by 1, can VectorPlot3D confine the vectors >> to a surface? >> >> Thanks, >> Dave Snead >> >> > >

**References**:**Re: vector/matrix indexed from zero***From:*Norbert Marxer <marxer@mec.li>

**VectorPlot on a Circle***From:*"Dave Snead" <dsnead6@charter.net>