Re: Drawing field Plot 3d

• To: mathgroup at smc.vnet.net
• Subject: [mg54781] Re: Drawing field Plot 3d
• From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
• Date: Tue, 1 Mar 2005 01:58:42 -0500 (EST)
• Organization: Uni Leipzig
• References: <cvumdf\$bof\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

a) can you write down equation in Mathematica syntax ? with some
parameters (like the interval of s[],v[] and i[]) where you
wish to draw the field ?
b)

deqn = {s'[t] == 100000 - 0.1*s[t] - 2.10^-7*s[t]*v[t],
v'[t] == 2.10^-7*s[t]*v[t] - 0.5i[t],
i'[t] == 100*i[t] - 5v[t]};

absfield = Sqrt[#.#] & [Last /@ deqn];

field = deqn /. a_ == b_ :> a == b/absfield;

fieldLineAt[x_, y_, z_] :=
Module[{ll},
ll = NDSolve[
Join[field, {s[0] == x, v[0] == y, i[0] == z}],
{s[t], v[t], i[t]}, {t, 0, 500}];
Cases[
ParametricPlot3D[Evaluate[
{s[t], v[t], i[t]} /. ll[[1]]],

{t, 0, 500},
DisplayFunction -> Identity], _Line, Infinity]
]

lines = fieldLineAt @@@ Table[Random[Real, {-1000, 1000}], {200}, {3}];

Show[
Graphics3D[lines]]

will draw the field lines at random points in the box {-1000,1000}^3

Regards

Jens

"win" <win at mipa.uns.ac.id> schrieb im Newsbeitrag
news:cvumdf\$bof\$1 at smc.vnet.net...
>I have a problem... about plotting field plot
> i have 3 silmultanous equation
> that is
> ds/dt=100000-0.1*s-2.10^-7*s*v
> dv/dt=2.10^-7*s*v-0.5i
> di/dt=100*i-5v
>
> i plotted the field plot with this
> ParametricPlot3D[{100000-0.1*s-2.10^-7*s*v,2.10^-7*s*v-0.5i100*i-5v
> },{x,0,1000000,},{y,0,1000000,},{z,0,1000000,},PlotStyle]
>
> i want to show the equirilibium point and show the field plot... so
> what kind of source program that i have to run...
> thank you
>
> best regard
> win
>

```

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