Among the scores of graphic packages available, `gnuplot` stands out
for its power and ease of use. Go to X and type `gnuplot`, and have
two sample data files ready: `2D-data.dat` (two data per line), and
`3D-data.dat` (three data per line).

Examples of 2-D graphs:

gnuplot> set title "my first graph" gnuplot> plot '2D-data.dat' gnuplot> plot '2D-data.dat' with linespoints gnuplot> plot '2D-data.dat', sin(x) gnuplot> plot [-5:10] '2D-data.dat' |

Example of 3-D graphs (each `row' of X values is followed by a blank line):

gnuplot> set parametric ; set hidden3d ; set contour gnuplot> splot '3D-data.dat' using 1:2:3 with linespoints |

A single-column datafile (e.g., a time series) can also be plotted as a 2-D graph:

gnuplot> plot [-5:15] '2D-data-1col.dat' with linespoints |

or as a 3-D graph (blank lines in the datafile, as above):

gnuplot> set noparametric ; set hidden3d gnuplot> splot '3D-data-1col.dat' using 1 with linespoints |

To print a graph: if the command to print on your Postscript printer is
`lpr -Pps file.ps`, issue:

gnuplot> set term post gnuplot> set out '| lpr -Pps' gnuplot> replot |

then type `set term x11` to restore. Don't get confused---the last print
will come out only when you quit `gnuplot`.

For more info, type `help` or see the examples in directory
`/usr/lib/gnuplot/demos/`, if you have it.