Ruby/gnuplot on windows

Using the sine wave example from the home page how to, I’ve been able to
get gnuplot to generate the plot but it immediately terminates, flashing
only briefly on the screen. I bypassed the which method and hardcoded
the executable in the gnuplot.rb starting at 44:

def Gnuplot.gnuplot( persist = true )
#cmd = which( ENV[‘RB_GNUPLOT’] || ‘gnuplot’ )
#cmd += " -persist" if persist
cmd = “C:\Gnuplot\pgnuplot.exe” + " -persist" if persist

It appears that the -persist flag is not being passed to the command
line. Any thoughts on how to get the -persist flat to function and keep
the graph active long enough for me to view it?