Hi, I am new to R and I need to solve the following problem: I have an ODE model with variables x(t) and y(t) that can be solved using the deSolve package. That model uses several parameters. Now I have a set of observations for y(t), denoted as Y(t). I need to optimize the value of these parameters such that error between the model output y(t) and the observation Y(t) is minimized. In another word, y(t) is fitted to Y(t) as much as possible. What R package is available to optimize these parameter? Is there any sample R codes available? Thank you very much for your help! Jiefeng