Re: PlotPoints in plot

*To*: mathgroup at smc.vnet.net*Subject*: [mg48581] Re: [mg48520] PlotPoints in plot*From*: DrBob <drbob at bigfoot.com>*Date*: Sat, 5 Jun 2004 07:20:06 -0400 (EDT)*References*: <200406040849.EAA23664@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

On my machine, at least, the count is 41: plot = Plot[Sqrt[1 - x^2], {x, -1, 1}, PlotPoints -> 3]; Length@Flatten[Cases[plot, Line[a__] :> a, Infinity], 1] 41 Help documentation on PlotPoints is obviously incorrect (again), or at least misleading (again). An adaptive procedure is used whether you want it or not, obviously. I suspect PlotPoints sets a MINIMUM number of points. Here's an attempt with only 4 points: plot = Plot[ Sqrt[1 - x^2], {x, -1, 1}, PlotPoints -> 3, PlotDivision -> 1, MaxBend -> 90]; Length@Flatten[Cases[plot, Line[a__] :> a, Infinity], 1] 4 Here again, the documentation for MaxBend is incorrect; increasing it should decrease the number of plot points, but... plot = Plot[ Sqrt[1 - x^2], {x, -1, 1}, PlotPoints -> 3, PlotDivision -> 1, MaxBend -> 100]; Length@Flatten[Cases[plot, Line[a__] :> a, Infinity], 1] 5 I'm thinking you'll have to pick your points manually, something like this: Show[Graphics[Line@Table[{x, Sqrt[1 - x^2]}, {x, -1, 1}]]] DrBob On Fri, 4 Jun 2004 04:49:37 -0400 (EDT), "G.L.Narasimham" <mathma18 at hotmail.com> wrote: > For the plot command Plot[Sqrt[1-x^2],{x,-1,1},PlotPoints->3] > I expected to see a triangle joining 3 points on a circle, but a > continuous line ( default PlotPoints->20? )appears. However, > ParametricPlot3D[{Cos[t],Sin[t],0},{t,0,Pi},PlotPoints->3,ViewPoint->{0,0,5}] > gives a triangle. How to get a polygon of straight sides in the > unparametered Plot? > > -- DrBob at bigfoot.com www.eclecticdreams.net/index.html

**References**:**PlotPoints in plot***From:*mathma18@hotmail.com ("G.L.Narasimham")