       Re: ContourPlot and ColorFunction Opacity

• To: mathgroup at smc.vnet.net
• Subject: [mg93755] Re: [mg93714] ContourPlot and ColorFunction Opacity
• From: "David Park" <djmpark at comcast.net>
• Date: Tue, 25 Nov 2008 07:15:35 -0500 (EST)
• References: <10198237.1227519579820.JavaMail.root@m02>

```There are several ways to do this. One method is to put the GridLines in
front.

ContourPlot[Cos[x y], {x, -\[Pi], \[Pi]}, {y, -\[Pi], \[Pi]},
GridLines -> Automatic,
RegionFunction -> Function[{x, y, z}, \[Pi] < x^3 + y^3 < \[Pi]^3],
BoundaryStyle -> Red,
ColorFunction -> "TemperatureMap",
Method -> {"GridLinesInFront" -> True}]

A second method is to write a fancier ColorFunction.

ContourPlot[Cos[x y], {x, -\[Pi], \[Pi]}, {y, -\[Pi], \[Pi]},
GridLines -> Automatic,
RegionFunction -> Function[{x, y, z}, \[Pi] < x^3 + y^3 < \[Pi]^3],
BoundaryStyle -> Red,
ColorFunction ->
Function[f, Opacity[.7, ColorData["TemperatureMap"][f]]]]

A third method, for those who have the Presentations package, is to simply
set the Opacity before drawing the contours.

Needs["Presentations`Master`"]

Draw2D[
{Opacity[.7],
ContourDraw[Cos[x y], {x, -\[Pi], \[Pi]}, {y, -\[Pi], \[Pi]},
RegionFunction -> Function[{x, y, z}, \[Pi] < x^3 + y^3 < \[Pi]^3],
BoundaryStyle -> Red,
ColorFunction -> "TemperatureMap"]},
GridLines -> Automatic,
Frame -> True]

David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark

From: alpinekarst [mailto:alpinekarst at gmail.com]

Dear All,

I am hoping that one of the Gurus here can help me figure out how to
adjust the opacity for a ContourPlot ColorFunction in Mathematica 6.0.3

say for example I have a 2D ContourPlot plot such as:

ContourPlot[Cos[x y], {x, -Pi, Pi}, {y, -Pi, Pi},
GridLines -> Automatic,
RegionFunction -> Function[{x, y, z}, Pi < x^3 + y^3 < Pi^3],
BoundaryStyle -> Red, ColorFunction -> "TemperatureMap"]

How can I adjust the Opacity of the filled region so that the
gridlines are somewhat visible within the boundary defined by the
RegionFunction?  Using a constant would be fine or even better some
generic decay function from the centroid of the region.

I have tried defining the opacity in the color function multiple ways
such as:
{Directive[Opacity[0.5]], ColorData["TemperatureMap"][#1] &}
but keep getting BoxForm and Graphics Directive errors.

I'm thinking of resorting to replacement rules against AbsoluteOptions
but that's bound to get ugly and I am hoping that there is a better
way? This is probably quite simple...but not for me today.

Thanks.

```

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