Re: Plotting two functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg78340] Re: Plotting two functions*From*: dh <dh at metrohm.ch>*Date*: Thu, 28 Jun 2007 06:28:54 -0400 (EDT)*References*: <f5vsai$kr6$1@smc.vnet.net>

Hi, if I understand correctly, you can numerically calculate X as a function of r and you would like to get the inverse r[X]? The simplest solution is to solve your original equation for r. This gives: X->(-gamma r-Pp r-beta r^3-Pp r^3-r^5)/(c+delta r^2+alpha r^4) You can also do it numerically. Calculate some {X,r} pairs covering the region needed, then feed it e.g. to Interpolation to get r[X]. hope this helps, Daniel SK wrote: > Hi > > I have a 5th order equation of the form > > eqntony445=r^5+(alpha*X)*r^4+(beta+Pp)*r^3+(delta*X)*r^2+(gamma+Pp)*r > +c*X==0 > > where alpha, beta, delta and gamma are other combination of terms that > I havent included for the sake of simplicity. > > I can plot X with respect to r for various values of Pp > > Plot[Evaluate[Table[X /. Flatten[Solve[eqntony445 == 0, X]], {Pp, 0, > 20, 5}]], {r, -0.5, 0.5}] > > The problem is I have another function of the form > > V=Integrate[ ((Pp)/(s)*((r^3+r)/(r^2+1)^2)+2*r,X] > > and need to plot it with respect to X. It keeps spitting out stuff of > the form Root, which is understandable for 5th order equations, but I > find that if I can plot V with respect to r then there must be a way I > can take those r values and translate them to X values. Any help will > be greatly appreciated. > Thanks > S > >