Re: Help !! plot roots of an expression
- To: mathgroup at smc.vnet.net
- Subject: [mg72428] Re: [mg72349] Help !! plot roots of an expression
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Wed, 27 Dec 2006 06:11:18 -0500 (EST)
- Reply-to: hanlonr at cox.net
poly=(w-w1) (w + 2 q +en^2 + s w^3) + r; Collect[poly,w] s*w^4 - s*w1*w^3 + w^2 + (en^2 + 2*q - w1)*w + r - en^2*w1 - 2*q*w1 soln=Transpose[{Re[w],Im[w]}/. {Reduce[poly==0/.{s->2,w1->1,en->5,r->3/2},w]//ToRules}]; Plot[#,{q,-22.5,0}, PlotStyle->{ {AbsoluteThickness[2],AbsoluteDashing[{3,10}],Red}, {AbsoluteDashing[{10,10}],Blue}, {AbsoluteThickness[2],AbsoluteDashing[{3,10}],Green}, {AbsoluteDashing[{10,10}],Orange}}, Frame->True,Axes->False, PlotRange->{{-22.6,0.1},Automatic}, ImageSize->400]&/@ soln; List@@(First/@Reduce[poly==0/. {s->2,w1->1,en->5,r->3/2},w,Reals])//N {q<-17.778,q==-17.778,q==-11.7695,q>-11.7695} Bob Hanlon ---- mintoo <varun.tangri at gmail.com> wrote: > I have a polynomial. A simple example is like this > > (w-w1) (w + 2 q +en^2 + s w^3) + r > The actual example is more complicated. It is a function of several > variables e.g. q, en, s, r etc.. > I also need to Collect & FullSimplify this expression. > Finally, from that result, I want to plot the roots of this polynomial > (imaginary & real part) vs. q (say) or vs en etc.. other variables can > be given fixed values. > > I'll the thankful if you give me hints how to do this!! >