/usr/share/doc/ruby-gsl/examples/alf/alf.gp is in ruby-gsl 2.1.0.3+dfsg1-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | set multiplot
set size 0.5, 0.5
set grid
set origin 0, 0.5
plot "alf.dat" u 1:2, sin(x)
set origin 0.5, 0.5
plot "alf.dat" u 1:3, 3*cos(x)*sin(x)
set origin 0, 0
plot "alf.dat" u 1:4, 3*sin(x)*sin(x)
set origin 0.5, 0
plot "alf.dat" u 1:5, 1.5*sin(x)*(5*cos(x)*cos(x)-1)
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