/usr/share/doc/ruby-gsl/examples/vector/decimate.rb 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 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | #!/usr/bin/env ruby
# Turn on warnings
$-w = true
require 'irb/xmp'
require 'gsl'
# Apparently, IRB::Frame has a bug that prevents the defaults from working, so
# an XMP instance must be created explicitly this way instead of using the
# otherwise convenient xmp method.
XMP.new(IRB::Frame.top(-1)).puts <<END
# Setup constants
N = 1000
DECIMATE1 = 10
DECIMATE2 = 100
# Setup random number generator
r = GSL::Rng.alloc
# Create Vector of x values
x0 = GSL::Vector.linspace(0, 20, N)
# Data: Bessel function + noise
y0 = GSL::Sf::bessel_J0(x0) + GSL::Ran::gaussian(r, 0.1, N)
# Decimate y0 by DECIMATE1
y1 = y0.decimate(DECIMATE1)
# Decimate y0 by DECIMATE2
y2 = y0.decimate(DECIMATE2)
# Create Vectors of decimated x values
x1 = GSL::Vector.linspace(0, 20, N/DECIMATE1)
x2 = GSL::Vector.linspace(0, 20, N/DECIMATE2)
# y1 and y2 are shifted vertically for visual purpose
GSL::graph([x0, y0], [x1, y1-1], [x2, y2-2])
END
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