There are several things that need to be correctly set before you can run plotdata. The Unix shell (the supervisor that interprets and performs your Unix commands) on spartan needs to be told what type of terminal you are on, what type of hardcopy output device you have, and where on the system disk are the files required by plotdata. Hopefully, your .login file has made these determinations for you. To check, issue the Unix command setenv; it will report the list of the so-called environment variables that are currently set. If you do not see the right definitions (see below), here's what you may need to type at the shell prompt, before starting up plotdata:
setenv TRIUMF_FONTS /usr/local/lib/triumf
setenv TRIUMF_TERMINAL_TYPE X
setenv TRIUMF_PLOTTER_TYPE POSTSCRIPT