Data Analysis on the Extra-solar Planets Using Robust Clustering
  We use both the conventional and more recently developed methods of cluster analysis to study the data of extra-solar planets. 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, on-going tidal and disc interaction, respectively. 
Ing-Guey Jiang (1), Li-Chin Yeh (2), Wen-Liang Hung (2), Miin-Shen   Yang (3) ((1)National Tsing-Hua University, Taiwan, (2)...