Hi, I have a system of 6 differential equations with unknown paramters. This paramters and the initial values are to be estimate later by a least square method, for example by using "minimize", based on measurements. Is it possible to solve the system with parameter and initial conditions in the same way as I can solve single differential equation? I give an example for 2 equations. For example f1(t,x,y,p) and f2(t,x,y,p) define the right site of the differential equation. T = 10 sec is the endpoint Now the solve block Given x'(t)=f1(t,x(t),y(t),p) x(0)=a y'(t)=f2(t,x(t),y(t),p) y(0)=b (F(p,a,b), G(p,a,b))^T = odesolve(x,y,t,T) This works for a single differential equation but I get an error for a system of differential equation. If I define all parameters explicitly, for example a=1, b=2, p is a vector of known values, the following code works very well. a=1 b=2 p=(3,4,5)^T Given x'(t)=f1(t,x(t),y(t),p) x(0)=a y'(t)=f2(t,x(t),y(t),p) y(0)=b (F, G)^T = odesolve(x,y,t,T) best regards and thanks for your help Uli
