We study certain plane graphs, called Newton graphs, representing a special class of dynamical systems which are closely related to Newton's iteration method for finding zeros of (rational) functions defined on the complex plane. These Newton graphs are defined in terms of nonvanishing angles between edges at the same vertex. We derive necessary and sufficient conditions -of purely combinatorial nature- for an arbitrary plane graph in order to be topologically equivalent with a Newton graph. Finally, we analyse the structure of Newton graphs and prove the existence of a polynomial algorithm to recognize such graphs.
Jongen, H. T., Jonker, P., & Twilt, F. (1991). On the classification of plane graphs representing structurally stable rational Newton flows. Journal of combinatorial theory. Series B, 51(2), 256-270. https://doi.org/10.1016/0095-8956(91)90041-H