Abstract
We use both the conventional and more recently developed methods of cluster analysis to study the data of extrasolar planets (exoplanets). Using the data set with planetary mass M, orbital period P and orbital eccentricity e, we investigate the possible clustering in the ln M, ln P, ln P-ln M, e and ln P-e spaces. There are two main implications: (1) mass distribution is continuous, and (2) orbital population could be classified into three clusters, which correspond to the exoplanets in the regimes of tidal, ongoing tidal and disc interaction, respectively. © 2006 RAS.