RE: Plotting an implicit function

*To*: mathgroup at smc.vnet.net*Subject*: [mg50584] RE: [mg50559] Plotting an implicit function*From*: "David Park" <djmp at earthlink.net>*Date*: Sat, 11 Sep 2004 06:44:35 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

David, Use r_ and M_ in the definition, and I prefer a definition as a function and not an equation so we can test evaluate or Plot the function for various cases. f[r_, M_] := 1 + (-1 - 0.03*M^2 + 1.2*M)*r - ((0.05*E^(r*M))/r - 0.05/r + E^(r*M)*(1 - 0.05*M)) The following seems to give the plot that you are looking for. I fixed the aspect ratio to get a better representation and also extended the M domain to obtain a better picture of the function. Needs["Graphics`ImplicitPlot`"] ImplicitPlot[f[r, M] == 0, {M, 0, 30}, {r, 0.0001, 0.03}, AspectRatio -> 1, Frame -> True, FrameLabel -> {M, r}]; David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: David Friskin [mailto:david.friskin at upe.ac.za] To: mathgroup at smc.vnet.net I have the following implicit function: f[r, M]=1 + (-1 - 0.03*M^2 + 1.2*M)*r - (0.05*E^(r*M)/r - 0.05/r + E^(r*M)*(1 - 0.05*M))==0 where r is a function of M i.e. r(M). I would like to plot r(M) vs M, for {M,0,20}. I tried using ImplicitPlot[{f[r,M] == 0},{M,0,20}], but Solve is having problems finding the roots to my function. Could someone help me with the code to do this, perhaps using FindRoot somehow? Thanks David P.S. r > 0