plot and animate data sets

 The ygraph tool graphs one-dimensional data or displays a time-series of
 one-dimensional data sets. It is an enhanced alternative to the xgraph
 utility and supports the same input format as xgraph. Additionally,
 ygraph features:
 .
  * animating multiple plots simultaneously and synchronously;
  * stepping back and forth through animations one frame at a time;
  * zooming, similar to xgraph but without opening a lot of new windows;
  * plotting derivatives;
  * subtracting plots;
  * convergence tests;
  * reading compressed files;
  * exporting images and animations.