Re: ContourPlot ColorFunction Question

*To*: mathgroup at smc.vnet.net*Subject*: [mg119457] Re: ContourPlot ColorFunction Question*From*: Heike Gramberg <heike.gramberg at gmail.com>*Date*: Sun, 5 Jun 2011 07:01:26 -0400 (EDT)

You need to specify ColorFunctionScaling -> False to prevent the coordinates from being rescaled: Plot[x /. Solve[x^2 + c == x, x], {c, -2, 2}, Frame -> True, Axes -> False, PlotRange -> {-2, 2}, AspectRatio -> 1, ColorFunction -> (If[#2 > 0, Red, Green] &), ColorFunctionScaling -> False] Heike On 4 Jun 2011, at 11:21, Jody Sorensen wrote: > Thanks for the suggestions. It's an improvement, but it still doesn't do what I think it should be doing. In this simple example: > > Plot[x /. Solve[x^2 + c == x, x], {c, -3, 2}, Frame -> True, > Axes -> False, PlotRange -> {-2, 2}, AspectRatio -> 1, > ColorFunction -> (If[#2 > 0, Red, Green] &)] > > the whole graph is drawn in red, whereas anything below the axis should be green. > > Any ideas? > > Jody Sorensen > > --- On Fri, 6/3/11, Bob Hanlon <hanlonr at cox.net> wrote: > > From: Bob Hanlon <hanlonr at cox.net> > Subject: [mg119452] Re: [mg119436] ContourPlot ColorFunction Question > To: mathgroup at smc.vnet.net, "Jody Sorensen" <jodo11 at yahoo.com> > Date: Friday, June 3, 2011, 7:26 AM > > > For ContourPlot, there is only one argument for ColorFunction. That argument is the contour levels. > > ContourPlot[x^2 + c - x, {c, -2, 2}, {x, -2, 2}, > ColorFunction -> (If[# > 0, Red, Green] &), > Contours -> {0}] > > Plot[ > Evaluate[x /. Solve[x^2 + c == x, x]], > {c, -2, 2}, > Frame -> True, > Axes -> False, > PlotRange -> {-2, 2}, > AspectRatio -> 1, > PlotStyle -> {Green, Red}] > > Plot[ > x /. Solve[x^2 + c == x, x], > {c, -2, 2}, > Frame -> True, > Axes -> False, > PlotRange -> {-2, 2}, > AspectRatio -> 1, > ColorFunction -> (If[2 #2 > 1, Red, Green] &)] > > > Bob Hanlon > > ---- Jody Sorensen <jodo11 at yahoo.com> wrote: > > ==================================================== > I'm new to this list and possibly out of my depth, but I'd appreciate any help on this issue. > > We are trying to plot an implicit function using ContourPlot and have the points on the curve colored based on the x and y values (which we call c and x) - specifically based on the value of the derivative. > > We have tried things like the following without success, even though similar commands work with Plot: > ContourPlot[x^2+c = x, {c, -2, 2}, {x, -2, 2}, > ColorFunction -> (If[2 #1 > 1, Red, Green] &)] > > Any suggestions or solutions would be great to hear! > > Thanks! > Jody Sorensen