Originally Posted by

**CaptainBlack** This is a first order system with state vector:

$\displaystyle X={X_1 \brack X_2}={x \brack s}$

with derivative:

$\displaystyle X'={\frac{0.25X_2X_1}{0.005+X_2} \brack \frac{0.45\times 0.25 X_2X_1}{0.005+X_2}}$

Now look up the help for ode45

CB

The function to eveulate the derivatives should look someting like:

Code:

function dx=derive(t,x)
dx=zeros(size(x));
dx(1)=0.24*x(1)*x(2)/(0.005+x(2));
dx(2)=0.45*0.24*x(1)*x(2)/(0.005+x(2));

But you give insufficient information to set up the initial conditions, what are s and x at t=0?

CB