Re: Re: Problem with RegionFunction

*To*: mathgroup at smc.vnet.net*Subject*: [mg88126] Re: [mg88084] Re: Problem with RegionFunction*From*: "W_Craig Carter" <ccarter at mit.edu>*Date*: Fri, 25 Apr 2008 05:30:30 -0400 (EDT)*References*: <fukern$s4l$1@smc.vnet.net> <fumqti$sc8$1@smc.vnet.net>

Hello Zac, This was explained to me the following way. WIthin Manipulate, the PerformanceGoal option switches from Speed to Quality when a manipulate variable stops changing. Thus, the change in appearance of Graphics3D objects while sliding. To handle the boundaries of a plot well, values are probed on either side of the boundary even though they are not going to appear on the final plot. PerformanceGoal as I understand it, changes the way that plot resolves the boundaries and thus your 0^0. I hope this explanation is not too far off the mark. WCC On Thu, Apr 24, 2008 at 5:56 AM, zac <replicatorzed at gmail.com> wrote: > Thank you for the answers. > > I understand that the case where x=0 and y=0 is undefined, but I don't > understand why does Mathematica compute this case when ranges are > given explicitely to avoid such situations? Why do I have to define > the regionfunction to exclude x=0 and y=0 (as Fred suggested it)? Is > it not trivial to exclude these as the PlotRange dictates it? Why is > it that the problem does not surface when I omit the Manipulate[...] > wrap? > Istvan > > > > On Apr 23, 10:10 am, Jens-Peer Kuska <ku... at informatik.uni-leipzig.de> > wrote: > > Hi, > > > > try > > > > Manipulate[ > > Plot3D[Sin[x]*Cos[y], {x, 1, 10}, {y, 2, 10}, > > RegionFunction -> Function[{x, y}, 45 <= (y^x)], > > Exclusions -> x == 0], {dummy, {True, False}}] > > > > because y^x for x==0 and y==0 is undefined. > > > > Regards > > Jens > > -- W. Craig Carter