Most of the plots of interferometric data in $\cal OYST\!ER\,$are handled by one procedure (plotdata). Consequently, there is one widget handling the plot selection (ww_plot). Whenever a plot is requested, a selection widget designed for that class of plot (point, scan, astrom, etc.) is opened, replacing any currently displayed selection widgets from previous requests. A second widget is created for the selection of which indices to plot, if this input is required. Plots can be 2-dimensional or 3-dimensional. Therefore, three data streams (`x', `y', and `z') are available.