Exclusions

*To*: mathgroup at smc.vnet.net*Subject*: [mg87978] Exclusions*From*: Fiona H Evans <fevans at agric.wa.gov.au>*Date*: Mon, 21 Apr 2008 06:39:44 -0400 (EDT)

I'm having a little trouble with the use of "Exclusions" for plotting. If I use "Exclusions -> Automatic" in the following, Plot3D finds no exclusions. pdfN[{x_, y_} := PDF[MultinormalDistribution[{0, 0}, {{1, 0}, {0, 1}}], {x, y}]; grayColors = Function[{x, y, z}, (Lighter[Gray, #] &)[z]]; Plot3D[ pdfN[{x, y}], {x, -3, 3}, {y, -3, 3}, PlotRange -> Full, Mesh -> 30, ColorFunction -> grayColors, PlotPoints -> 50, Exclusions -> Automatic, ExclusionsStyle -> {None, Directive[Thick, Red]}, MaxRecursion -> 0, AxesLabel -> {"x", "y"}] However, if I try to exclude a cross-section through the mean of the distribution asin the following, as well as my defined Exclusions, I get an exclusion drawn at {y == 0, x < 0}, even though I have used inequalities to exclude y == 0 from my Exclusions. Plot3D[ pdfN[{x, y}], {x, -3, 3}, {y, -3, 3}, PlotRange -> Full, Mesh -> 30, ColorFunction -> grayColors, PlotPoints -> 50, Exclusions -> {{ArcTan[x, y] == 0.5, x > 0 && y > 0}, {ArcTan[x, y] == -Pi + 0.5, x < 0 &7 y < 0}}, ExclusionsStyle -> {None, Directive[Thick, Red]}, MaxRecursion -> 0, AxesLabel -> "x", "y"}] Can anyone see a way that I can avoid this? Regards, Fiona.