Welcome to Linux Questions.
man xgraph
http://hpux.connect.org.uk/hppd/hpux...-12.1/man.html
Xgraph documentation
http://www.xgraph.org/
Example, using the 'xgraph' inside ns-allinone :
'cd ns-allinone-2.33/xgraph/'
'
./xgraph examples/xgtest.xg'
( using example file in 'ns-allinone-2.33/xgraph/examples/' )
....