As a note, to get it to run on windows I had to replace
which(ENV['GNUPLOT'] || gnuplot)

with
which(ENV['GNUPLOT'] || gnuplot) || 'gnuplot'
for whatever reason.
perhaps which was looking for gnuplot not gnuplot.exe
Cheers!
=r

Date: 2009-07-16 13:02
Sender: Roger Pack

if this is still a problem could you file an issue at 
http://github.com/rogerdpack/ruby_gnuplot/tree/master ? 
(though not the original creator, I'm going to upkeep a 
maintained branch there).
Thanks

Date: 2009-07-08 19:35
Sender: Roger Pack

It might could also raise if it which returns null.
=r