  In this paper, a down-to-earth approach to purely data-based modelling of
unknown dynamical systems is presented. Starting from a classical, explicit ODE
formulation $y' = f(t,y)$ of a dynamical system, a method determining the
unknown right-hand side $f(t,y)$ from some trajectory data $y_{k}(t_{j})$,
possibly very sparse, is given. As illustrative examples, a semi-standard
predator-prey model is reconstructed from a data set describing the population
numbers of hares and lynxes over a period of twenty years, and a simple damped
pendulum system with a highly non-linear right-hand side is recovered from some
artificial but very sparse data.
