Many modern data analysis problems in both industry and academia involve building a model that can predict the future based on historical variables. The 2009 KDD Cup was an international data mining competition devoted to this type of problem, where contestants attempted to predict the behaviour of mobile phone customers using an extensive database of historical information. The University of Melbourne team managed to win one part of this challenge, using R almost exclusively. In this talk I’ll give some background to the area and the specific problem, and discuss how we went about building our models. The talk will be fairly accessible, and deal with many of the practical issues encountered in this type of work.