ode 45 plot of intermediate vraibles of differential equations

clear all

clc;

Tspan =[0 1];

X0=[1.0; 1]; % Initial condition

%solving the differential Equation

[t,x]=ode45(@myfunc,Tspan,X0);

%Plotting the figures figure(1)

subplot(2,1,1)

plot(t(:,1),x(:,1))

xlabel('t');

ylabel('x1');

grid on

subplot(2,1,2)

plot(t(:,1),x(:,2))

xlabel('t');

ylabel('x2')

grid on

% subplot(3,1,3) % plot(t(:,1),P) % xlabel('t'); % ylabel('P') % grid on

The ode function is:

function dv=myfunc(t,x)

P=sqrt(x(1)+x(2));

%The Diffenrential Equation 

        dv=[ (x(1))+(x(2)*x(2))+P;%x1dot Equation
          x(1)-x(2); ]; % x2dot Equation

I want to plot P also wrt time like x1 and x2.

Since the ode fucntion returns only the time and solution ie t and x (x1,x2) . How to get the P for plotting?.I tried declaring it global but in vein .Please help

Answer 1

[Mischa Kim]

Thayumanavan, after the ode45 call, compute P:

[t,x]=ode45(@myfunc,Tspan,X0);

P = sqrt(x(:,1) + x(:,2));
plot(t,P)

[Thayumanavan]

Thanks sir.I Got the plot.