Re: Documentation on (Color) Blend

*To*: mathgroup at smc.vnet.net*Subject*: [mg111271] Re: Documentation on (Color) Blend*From*: "David Park" <djmpark at comcast.net>*Date*: Mon, 26 Jul 2010 06:35:26 -0400 (EDT)

For DensityPlot, the value of the argument supplied to the ColorFunction is f, the plot function value. This is in the ColorFunction notes. In this case it is x. You can use Rescale to control the domain of x that maps into 0 to 1. DensityPlot[x, {x, -2, 3}, {y, 0, 1}, FrameTicks -> None, ColorFunction -> (Blend[{Red, Green}, Rescale[#, {-2, 3}]] &), ColorFunctionScaling -> False] If you evaluate the Help example you will see that the original output shown is incorrect and one actually gets what you do get. This must be a case where WRI updated the function but not the Function page. The following maps 0 < x < 1 to the full Blend range, and values of x outside the domain go to the limiting color. DensityPlot[x, {x, -2, 3}, {y, 0, 1}, FrameTicks -> None, ColorFunction -> (Blend[{Red, Green}, Rescale[#, {0, 1}]] &), ColorFunctionScaling -> False] David Park djmpark at comcast.net http://home.comcast.net/~djmpark/ From: telefunkenvf14 [mailto:rgorka at gmail.com] Group: The documentation on Blend[], in the "Possible Issues" section, contains the following example. ---------------- In plot functions, use ColorFunctionScaling to control global scaling of variables: Table[DensityPlot[x, {x, -2, 3}, {y, 0, 1}, FrameTicks -> None, ColorFunction -> (Blend[{Red, Green}, #] &), ColorFunctionScaling -> t], {t, {False, True}}] ---------------- I noticed that when I evaluate the code, the original output is not reproduced. On my machine the new plots look exactly the same. (Windows 7, 64-bit, Mathematica 7.0.1) Can someone offer a fix? My goal is to generate a Green to White to Red spectrum with a 'fuzzier' center; eventually I'll use this for coloring a map. -RG