Define a function as a graphics directive?

*To*: mathgroup at smc.vnet.net*Subject*: [mg105020] Define a function as a graphics directive?*From*: Porscha Louise McRobbie <pmcrobbi at umich.edu>*Date*: Wed, 18 Nov 2009 06:58:03 -0500 (EST)

Hi, I have a very simple contour plot: ContourPlot[ z Exp[-Sqrt[z^2 + x^2]/2.], {x, -10, 10}, {z, -10, 10}, ContourShading -> None, Contours -> 15, ContourStyle -> {{Black, Thick}}] I do not want the plot shaded, but I want to color the contour lines according to a function of z (e.g., Sign[z], where z>0 is black, z<0 is red). Can this be done within ContourStyle? I tried putting a function definition for the color inside ContourShading, but I get an error since it's not a graphics directive (and it's my understanding that ColorFunction is only for shading the regions between contours). Thanks for any input! Porscha