VWhere: A Visual, Extensible `where' Command
  In this paper we describe "VWhere," a S-Lang guilet which augments the computational power of "where" with the point-click ease of a Gtk-based visual interface. The result is a new mechanism for interacting with datasets, which unifies the constraint evaluation cycle implicit within observational analysis and provides a number of compelling advantages over traditional tool-based methods. 
Michael S. Noble