Frequently Asked Questions
From PLplotWiki
My program exits with the error message Unable to either (1) open/find or (2) allocate memory for the font file
The PLplot library can't find the font files plstnd5.fnt and plxtnd5.fnt. Set the environment variable PLPLOT_LIB to the directory where these files are, e.g. export PLPLOT_LIB=/usr/local/plplot/data.