Returning several dataset using ode45

2021 12 7
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更新时间：2021 12 8
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Hi. I have a problem where I want an ode45 function to return 5 dataset using the code
clc; clear; close all;
% Defining parameters and initial conditions
f = 0.35;
r = [0.3:0.3:1.5];
zeta = 0.25;
Theta0 = [0.30, 0];
tspan = [0 10];
% Solver options
opts = odeset('RelTol',1e-6,'AbsTol',[1e-9 1e-9]);
% Solver
[t,theta] = ode45(@(t,theta) odefcn(t,theta,f,r,zeta), tspan, Theta0);
plot(theta(:,1),theta(:,2));
As you can see, r is a parameter in the function and I want to create a plot for each of the values for r. The code is running fine when using a single value for r but breaks when using a vector.

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VBBV
VBBV 2021-12-7

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for i = 1:length(r)
[t,theta] = ode45(@(t,theta) odefcn(t,theta,f,r,zeta), tspan,Theta0);
plot(theta(:,1),theta(:,2));hold on;
end
Use a for loop and try it

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Walter Roberson
Walter Roberson 2021-12-8
for i = 1:length(r)
[t,theta] = ode45(@(t,theta) odefcn(t,theta,f,r(i),zeta), tspan,Theta0);
plot(theta(:,1),theta(:,2));hold on;
end
No it still gives me an error. Just to be sure I have incorporated it correctly, was this what you meant?
clc; clear;close all;
% Defining parameters and initial conditions
f = 0.35+0.1;
r = [0.3:0.3:1.5];
zeta = 0.25;
Theta0 = [0.30, 0];
tspan = [0 1000];
% Solver options
opts = odeset('RelTol',1e-6,'AbsTol',[1e-9 1e-9]);
% Solver
for i = 1:length(r)
[t,theta] = ode45(@(t,theta) odefcn(t,theta,f,r,zeta), tspan,Theta0);
plot(theta(:,1),theta(:,2));hold on;
end
I will just include the function file as well for good measure
function dthetadt = odefcn(t,theta,f,r,zeta)
dthetadt = zeros(2,1);
dthetadt(1)=theta(2);
dthetadt(2)=f.*sin(r.*t)-2.*zeta.*theta(2)-sin(theta(1));
end
I got it working now. Thank you!

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