Src of any simple data plotting graphic program under X-Windows needed

[thor]

Hello!

I need some specialized program that should just read a data file and 
plot it in X-windows. No dependencies, no toolkits - just an absolutely 
bare minimum. I just have neither a disk space on target system for any 
specialized toolkits nor time to study them.

(Really, the existence of Windows closed source program is the only 
thing that keeps us under Windows XP).

Long time ago (some 20 years or so) in FreeBSD 3 times I used a 
primitive program named xperfmon3 that plotted the current processor use 
etc but it expired due to absence of a maintainer and I cannot find it.

Are there in port tree any similar simple programs that could be used as 
a prototype?

Yours sincerely

Anatoly