Re: ugly Plot Eigenvalues ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg39667] Re: ugly Plot Eigenvalues ?*From*: BobHanlon at aol.com*Date*: Sat, 1 Mar 2003 02:47:26 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

In a message dated 2/28/03 9:05:34 AM, Pavel.Pokorny at vscht.cz writes: > How can I plot Re Eigenvalues as a function of a parameter > without unwanted ugly connections between branches? > In the example (computed by Mathematica 4.2 for HP-UX PA-RISC) > > m1={{8., 8, 7}, {0, 5, 5}, {8, 0, 0}} > m2={{6., 0, 6}, {10, 8, 3}, {5, 8, 6}} > Plot[Evaluate[Re[Eigenvalues[m1+w*m2]]], {w,-3,3}]; > > for w approximately -0.4 there is an unwanted vertical bar. > This is related to "ordering" of solutions to equation. > > Is there a simple nice solution for this and related examples? > (taking exact numbers in the example above avoids the unwanted connection, > but this is not a good solution for a general machine precission problem) > One approach is just to avoid the ordering issue by using a high density ListPlot m1={{8.,8,7},{0,5,5},{8,0,0}}; m2={{6.,0,6},{10,8,3},{5,8,6}}; ListPlot[Flatten[Table[ {w, #}& /@ Re[Eigenvalues[m1+w*m2]], {w, -3, 3, .01}], 1], Frame -> True,Axes -> False, PlotRange -> {-20, 20}, PlotStyle -> {AbsolutePointSize[1]}]; Bob Hanlon