Retrieve vector within function file

Question

prabhjeet singh 2021-3-31

评论： prabhjeet singh 2021-3-31

x = 10';
tspan = [0 10];
[t,x]= ode45(@fun,tspan,x);
[~, u] = fun(t.',x.');
figure(1)
plot(t,u,'-k','Linewidth',1.5);

and function file is

function [dot,u] = fun(~,x)
k = 1;
p = 10;
x = x(1);
u = (-k.*x + x.^3 - p.*x^2) ./ x;
xdot = -x.^3 + p.*x.^2 + x.*u;
dot = xdot';

When I try to plot t with u, I am not getting a plot because input u is not getting saved as vector.

Is there any way that u can be saved as a vector here?

Thanks

Answer 1

VBBV 2021-3-31

function [dot,u] = fun(~,x)
k = 1;
p = 10;
%x = x(1);
x
u = (-k.*x + x.^3 - p.*x.^2) ./ x;
xdot = -x.^3 + p.*x.^2 + x.*u;
dot = xdot';

VBBV 2021-3-31

编辑：VBBV 2021-3-31

Comment the line

%x = x(1);

Rune it again with a small change below line in function

u = (-k.*x + x.^3 - p.*x.^2) ./ x; % need element wise power operator

prabhjeet singh 2021-3-31

Thankyou very much VBBV. :)