[ns] xgraph won't work?

["nicky-muhammad ali" <nickyma@telkom.net>]

hello mr lloyd and ns-users, here i have some problem about
running a ns example.
iam a new user.
ns failed to load graphical and plotting of a tracing data
on my linux rh6.2 machine with source
ns-allinone-2.1b7a.tar.gz. ns success in making the .tr
(tracing) file but like i've describe before there's no
xgraph data plot.
why is it happended? is it because the xgraph is failed when
first installation. if it is, how can i install it
separately?because i've already had the xgraph source.

please forward my letter, ok . thank you for all
best regards,

nicky muhammad ali
telecommunication engineering
stttelkom
bandung
indonesia