Hi Nicia
1.
t is just a parameter, not the reference vector of the differential equation.
the output of ode45() is not
but
.
2.
There are other more efficient ways to use ode45, but a way to have it running is
clear all;clc;close all;
x=[2:.01:5];
t=[-100 .5 20 1e3];
options=optimset('Display','off');
x_span=[2 5];
figure(1); hold all
for k=1:1:numel(t)
t1=t(k);
f1=@(t1,x) 1/((.75*t1)*x^-3+(.5*t1^2)*x^-5);
[X,Y]=ode45(f1,x_span,0.7,options)
hold all; plot(X,Y)
end
grid on
.
3.
Perhaps a 'better picture' of the beahviour is obtained when expanding the range
x=[-20:.01:50];
x_span=[-20 50];
figure(2); hold all
for k=1:1:numel(t)
t1=t(k);
f1=@(t1,x) 1/((.75*t1)*x^-3+(.5*t1^2)*x^-5);
[X,Y]=ode45(f1,x_span,0.7,options)
hold all; plot(X,Y)
end
grid on
.
4.
Also, integration required, because of the dydx, than then would be
clear all;clc;close all;
x=[2:.01:5];
t=[-100 .5 20 1e3];
options=optimset('Display','off');
x_span=[2 5];
figure(1); hold all
for k=1:1:numel(t)
t1=t(k);
f1=@(t1,x) 1/((.75*t1)*x^-3+(.5*t1^2)*x^-5);
[X,Y]=ode45(f1,x_span,0.7,options)
hold all; plot(X,cumsmum(Y))
end
grid on
5.
and integrating the wider range
x=[-20:.01:50];
x_span=[-20 50];
figure(2); hold all
for k=1:1:numel(t)
t1=t(k);
f1=@(t1,x) 1/((.75*t1)*x^-3+(.5*t1^2)*x^-5);
[X,Y]=ode45(f1,x_span,0.7,options)
hold all; plot(X,cumsum(Y))
end
grid on
.
.
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thanks in advance
John BG
