Key points are not available for this paper at this time.
We describe the numerical techniques which enable us to estimate eigenfrequencies and rough eigenmodes from computer simulations of stellar discs. We show that the method works well, by comparing results from the N-body model with those available from linear theory in a particularly simple case. We give two further examples to illustrate the power and limitations of our methods.
Sellwood et al. (Tue,) studied this question.