Global variables to plot variables from ODE45 function
2 views (last 30 days)
Show older comments
Hello,
the following code stands representative for a bigger code, in which i want to plot some variables over time that are calculated in the odefunction but are gonna be passed to the ODE solver. Is there any way to set these variables as global variables, so that I can plot them outside of the ode Function?
Like in this case to plot the variable "a", which is calculatet inside the function.
tspan= 0:.01:10;
x=1;
[t,x] = ode45(@(t,x) odefcn(x,t),tspan,x);
figure;
plot(t,a);
function [dxdt] = odefcn(x,t)
a=cos(t)*x;
dxdt = x*a;
end
0 Comments
Answers (1)
Torsten
on 7 Sep 2023
Edited: Torsten
on 7 Sep 2023
t < pi/2 is necessary:
syms t x(t)
eqn = diff(x,t) == x^2*cos(t);
conds = x(0)==1;
dsolve(eqn,conds)
tspan= 0:.01:10;
x=1;
[t,x] = ode45(@(t,x) odefcn(x,t),tspan,x);
a = zeros(size(t));
for i = 1:numel(t)
[~,a(i)] = odefcn(x(i),t(i));
end
figure;
plot(t,a);
function [dxdt,a] = odefcn(x,t)
a=cos(t)*x;
dxdt = x*a;
end
6 Comments
Torsten
on 14 Sep 2023
Change the code according to your needs:
t = 0:1:100;
x = [t.',t.^2',t.^3']
a = zeros(3,numel(t));
for i = 1:numel(t)
[~,a(:,i)] = odefcn(x(i,:),t(i));
end
plot(t,a(2,:))
function [dxdt,vrv] = odefcn(x,t)
rv = [1;1;1];
delta = 0;
vrv = [cos(x(3)+delta) sin(x(3)+delta) 0;
-sin(x(3)+delta) cos(x(3)+delta) 0;
0 0 1]*rv;
end
See Also
Categories
Find more on Annotations in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!