The R-script grind.R is a wrapper around the deSolve, rootSolve and FME R-libraries making it very easy to perform phase plane analysis and fit ODE models to data. Make sure that the libraries deSolve, rootSolve and FME are installed, source the grind.R script and then run any of the models provided here. See the tutorial.pdf in the grindR directory for a full manual. Enjoy Rob de Boer