  We develop a numerical approach to reconstruct the phase dynamics of driven
or coupled self-sustained oscillators. Employing a simple algorithm for
computation of the phase of a perturbed system, we construct numerically the
equation for the evolution of the phase. Our simulations demonstrate that the
description of the dynamics solely by phase variables can be valid for rather
strong coupling strengths and large deviations from the limit cycle. Coupling
functions depend crucially on the coupling and are generally non-decomposable
in phase response and forcing terms. We also discuss limitations of the
approach.
