Solving differential equations involving heaviside function.

I have a set of differential equations involving heaviside function. I want to solve it numerically using ode45, however on solving I get all values of y as NaN. But the the derivative functions are not NaN. I think something is going wrong inside ode45. Can anyone guide on how to solve ODEs involving heaviside function using ode45? Please give suitable code snippets if possible.

Answer 1

[Alan Stevens]

Here's a snippet that works, but it would be better if you uploaded your code, as we stand a better chance of solving your problem that way:

tspan = [0 2];
ic = 1;
[t, y] = ode45(@fn, tspan, ic);
plot(t,y),grid

function dydt = fn(t,y)
         u = heaviside(t-1);
         dydt = -u*y;
end