Gr is a visualization and analysis application for displaying, editing, and printing X-Y data. It can be used to display or ani-mate vector data, particle paths, or two-dimensional (2D) data fields, but only the data-series interface is described in this docu-ment. Gr works with any data series that describes Y as a function of X, that is an ordered set of X-Y pairs. These pairs could represent points in space or form a time series, which is an ordered set of time-value pairs. Gr allows the user to zoom in and out and pan within a graph. It also offers several ways to edit or manipulate data, and can accept data in several file formats.