Astrostatistics is spreading through the field of astrophysics at an increasing pace. Astronomers realize that they can benefit from sophisticated tools to analyse their data, but they are not trained to this new way of thinking. This book is the result of a first one-week school organised in October 2013 in Annecy (France) during which statisticians tought many aspects of the regression to astronomers. The regression is the art to predict or explain a variable that is called dependent, to be predicted or explained, from variables that are called independent, predictive or explicatives. This theme is central in astrophysics where the data analysis, the understanding of the different parameters and observables, and the fitting to models, are ubiquitous. Many examples and practical sessions were given using the R-package. This school gave the opportunity for the two communities, statistics and astrophysics, to meet and discuss.