Hi Arnau,
try adapting this script. I guess th is x and dth is y in your
notation. You also need to write fun.m to give dx in terms of x=[th;dth] -
equivalent to your f&g functions rolled into one.
Peter.
dt = 0.1;
TH = [-1:0.1:1];
DTH = 5*[-1:0.1:1];
N = length(TH);
M = length(DTH);
i=0;
THETA = zeros(N*M,1);
DTHETA = zeros(N*M,1);
D_THETA = zeros(N*M,1);
D_DTHETA = zeros(N*M,1);
for th=TH
for dth=DTH
i++;
x = [th;dth];
dx = fun(x);
D_DTHETA(i) = dx(1);
D_THETA(i) = dx(2);
THETA(i) = th;
DTHETA(i) = dth;
endfor
endfor
M = [THETA DTHETA D_THETA*dt D_DTHETA*dt];
gset nokey
axis([min(TH), max(TH), min(DTH), max(DTH)]);
ylabel("$\\dot{\\theta}$")
xlabel("$\\theta$")
grid on;
gplot M with vector
From: Arnau Mir Torres <address@hidden>
Subject: phase portrait
Date: Mon, 21 Feb 2005 15:36:45 +0100
Hello.
I want to plot a phase portrait for a system of differential equations
of the form:
xdot= f(t,x,y)
ydot= g(t,x,y)
where t is the independent variable.
I want to plot in the x-y plane coordinates the phase portrait of the
previous differential equation.
Somebody can tells me if there exists a package or a script in octave
that does it?
Thanks in advance,
Arnau.
--
Arnau Mir Torres
Director Departament Matemàtiques i Informàtica.
Universitat de les Illes Balearss.
Edifici A. Turmeda, Campus de la UIB.
Crta. de Valldemossa, km. 7,5.
07122 Palma de Mallorca.
Baleares.
Spain.
Phone: +34 971 172987
Fax: +34 971 173003
e-mail: address@hidden
web: http://dmi.uib.es/~arnau
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