MATLAB: Not getting expected graph. Only straight lines are coming but there should be curve .

2dgraphMATLABmatlab functionodeode45plot

clc
tspan = (0:0.25:100);
y0 = [1376000000,10,0];
[t,y] = ode45(@(t,y)[-3.6*10^-9*y(1)*y(2)+0*y(3);-3.6*10^-9*y(1)*y(2)-0.5*y(2);0.5*y(2)-0*y(3)],tspan,y0);
plot(t,y(:,1),'b',t,y(:,2),'r',t,y(:,3),'g')

Best Answer

The values of the first component of the solution are so much larger in magnitude than the others that even if they did vary (which they do at first before settling down into what looks to be a steady state after about t = 2 or t = 3) it would be like trying to see one Lego block on the ground from the window of an airplane cruising at 30,000 feet.

If you plot the three components separately you can see the variation at the start.

figure
subplot(3, 1, 1);
plot(t, y(:, 1), 'b');
subplot(3, 1, 2);
plot(t, y(:, 2), 'r');
subplot(3, 1, 3);
plot(t, y(:, 3), 'g')

Related Solutions

MATLAB: Solving a nonlinear ODE using ode45

There is nothing wrong with your ODE except that it takes off to infinity at about t=3. You have to decide if this is appropriate behaviour of if you need to change it.

To see its behaviour, plot it:

f = @(t,y) [y(2); y(3); -y(3)-y(2)-y(1)+y(1)^2];
[t,y] = ode45(f,[0 30],[1;5;10]);
figure(1)
semilogy(t, y)
grid

MATLAB: How to plot signal for equation given below

Try this

t = linspace(0, 10, 100);
w = 1;
a = 1;
y1 = sin(w*t)./t;
y2 = sin(a*t).*sinh(a*t)./(2*a^2);
y3 = (exp(-t)+exp(-3*t)).*heaviside(t);
subplot(3,1,1)
plot(t, y1)
subplot(3,1,2)
plot(t, y2)
subplot(3,1,3)
plot(t, y3)

Best Answer

Related Solutions

MATLAB: Solving a nonlinear ODE using ode45

MATLAB: How to plot signal for equation given below

Related Question