RE: ugly Plot Eigenvalues ?
- To: mathgroup at smc.vnet.net
- Subject: [mg39717] RE: [mg39670] ugly Plot Eigenvalues ?
- From: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>
- Date: Mon, 3 Mar 2003 23:48:50 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
>-----Original Message----- >From: Pavel Pokorny [mailto:Pavel.Pokorny at vscht.cz] To: mathgroup at smc.vnet.net >Sent: Friday, February 28, 2003 10:46 AM >To: mathgroup at smc.vnet.net >Subject: [mg39717] [mg39670] ugly Plot Eigenvalues ? > > > Dear Mathematica friends, > >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) > >-- >Pavel Pokorny >Math Dept, Prague Institute of Chemical Technology >http://staffold.vscht.cz/mat/Pavel.Pokorny > A suggestion: ev = Re[Eigenvalues[m1 + w*m2]]; evs := Sort[ev] Plot[{evs[[1]], evs[[2]], evs[[3]]}, {w, -3, 3}] Of course a problem of reference still remains. -- Hartmut Wolf