Using xgraph
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(1) Create an xgraph data file that lists some number of data sets (one per 
    curve).  A data set contains an ordered pair of X Y coordinates, each point 
    on a separate line.  The name of the data set can be specified by a line
    beginning with a double quote.  Here is an example data file:

		"data set 1
		1  2
		2  4
		3  8
		4  16

		"data set 2
		1  1
		2  4
		3  9
		4  16


(2) To get xgraph to graph this data run:

	xgraph data_file 

(3) In addition, xgraph has all kinds of command line options for setting
    the scale of the graph, for specifying titles and labels...

     try:

	xgraph -bar data_file
	xgraph -lny data_file 		      # specifies log scale Y axis
	xgraph -lx 4,6 -ly 16,50 data_file    # zoom into part of the graph

    look at the man page for more options