Functions for creating plots and image files in a unified way regardless of
output format (EPS, PDF, PNG, SVG, TIFF, WMF, etc.). Default device options as
well as scales and aspect ratios are controlled in a uniform way across all
device types. Switching output format requires minimal changes in code. This
package is ideal for large-scale batch processing, because it will never leave
open graphics devices or incomplete image files behind, even on errors or user
interrupts.
