Re: piecewise and if

*To*: mathgroup at smc.vnet.net*Subject*: [mg128630] Re: piecewise and if*From*: Bob Hanlon <hanlonr357 at gmail.com>*Date*: Sun, 11 Nov 2012 01:28:08 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net*References*: <20121110070852.CB7D86968@smc.vnet.net>

Or perhaps more straightforwardly, set exclusions to none: Plot3D[g[x, y], {x, -1, 1}, {y, -1, 1}, Exclusions -> None] Bob Hanlon On Sat, Nov 10, 2012 at 11:30 AM, Bob Hanlon <hanlonr357 at gmail.com> wrote: > You can use ExclusionsStyle > > f[x_, y_] := Exp[-1/(x^2 + y^2)]; > > g[x_, y_] := Piecewise[{{0, x == 0 && y == 0}}, f[x, y]]; > > Plot3D[g[x, y], {x, -1, 1}, {y, -1, 1}, > ExclusionsStyle -> Lighter[Gray, .5]] > > > Bob Hanlon > > > On Sat, Nov 10, 2012 at 2:08 AM, Jon Joseph <josco.jon at gmail.com> wrote: >> I think these two functions should be the same but their plots show a clear difference: >> >> f[x_, y_] := Exp[-1/(x^2 + y^2)] (* this function undefined at (0,0) *) >> >> g[x_, y_] := Piecewise[{{0, x == 0 && y == 0}}, f[x, y]] (* Redefine so the hole is plugged *) >> >> h[x_, y_] := If[x == 0 && y == 0, 0, f[x, y]] (* Another, I think, equivalent way to redefine f[x, y] *) >> >> On my machine, "8.0 for Mac OS X x86 (64-bit) (October 5, 2011)" >> >> when I >> >> Plot3D[g[x, y], {x, -1,1}, {y, -1,1}] >> >> Plot3D[h[x, y], {x, -1,1}, {y, -1,1}] >> >> I see clear gaps along y=0 and x=0 for the g[x, y] plot and h[x, y] works properly. Am I misusing Piecewise? >> >> Thanks, Jon. >> >> >>

**References**:**piecewise and if***From:*Jon Joseph <josco.jon@gmail.com>