Extending the GGobi pipeline with rggobi ============================= The recently redesigned GGobi pipeline is a set of interconnected modules called stages. Clients may create custom GGobi visualizations by changing the modular composition of the pipeline. For example, the ggvis plugin extends the pipeline to perform multi-dimensional scaling on a dataset. The implementation of the pipeline is based on the GObject system from the GTK+ project. rggobi, a link from R to GGobi, gives R complete control over the GGobi pipeline. Besides support for constructing a pipeline from existing stages, rggobi enables the implementation of new pipeline stages in R. The R programmer need only provide a set of R callbacks that satisfies the contract for a stage implementation. Despite the performance trade-off, R is a convenient platform for the rapid prototyping of visualizations, because of its high-level nature and strong support for data analysis. rggobi users may customize interactive multivariate visualizations on-the-fly in support of an analysis. This functionality is based on a new RGtk2 feature that allows the extension of any GObject class from R. As an example, we extend GGobi to support interactive graph layout based on a system implemented in R. Michael Lawrence