Visualisation of Regression Trees

The regression tree [1] has been used as a tool for exploring multivariate data sets for some time. As in multiple linear regression, the technique is applied to a data set consisting of a continuous response variable y and a set of predictor variables {x1, x2, ..., xk} which may be continuous or categorical. However, instead of modelling y as a linear function of the predictors, regression trees model y as a series of ‘if-then-else’ rules based on values of the predictors. For example consider a data set of details of house sales with the following variables