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require 'test_helper'
class Spline2dTest < GSL::TestCase
def saddle(x,y)
x*x - y*y
end
def setup
x_samples =(-20..20).map(&:to_f).to_a
y_samples = (-20..20).map(&:to_f).to_a
z_samples = []
x_samples.each do |x|
y_samples.each do |y|
z_samples << saddle(x,y)
end
end
@x_array = GSL::Vector.alloc(x_samples)
@y_array = GSL::Vector.alloc(y_samples)
@z_array = GSL::Vector.alloc(z_samples)
@i2d_bicubic = GSL::Spline2d.alloc(GSL::Interp2d::BICUBIC,
@x_array, @y_array, @z_array)
@i2d_bilinear = GSL::Spline2d.alloc(GSL::Interp2d::BILINEAR,
@x_array, @y_array, @z_array)
end
def test_info
str = <<-EOF
Class: GSL::Spline2d
SuperClass: GSL::Object
Type: bilinear
xmin: -20.000000
xmax: 20.000000
ymin: -20.000000
ymax: 20.000000
xSize: 41
ySize: 41
EOF
assert_equal str, @i2d_bilinear.info
end
def test_use_case_saddle_interpolation
tolerance = 0.05 # 5% inaccuracy is tolerated in tests below
interpolator_type = GSL::Interp2d::BICUBIC
i2d = GSL::Spline2d.alloc(interpolator_type, @x_array, @y_array, @z_array)
# confirm that the fit passes very close to the sampled data points
@x_array.each do |x|
@y_array.each do |y|
expected_z = saddle(x,y)
z = i2d.eval(x, y)
error = (z - expected_z).abs
max_error = (expected_z.abs)*tolerance
if max_error == 0
max_error = tolerance
end
refute error > max_error, "error @ sample #{x},#{y} z: #{z} expected_z: #{expected_z}"
end
end
interstitial_x_values = @x_array.to_a.first(@x_array.size-1).map {|v| v+ 0.5}
interstitial_y_values = @y_array.to_a.first(@y_array.size-1).map {|v| v+ 0.3}
# confirm that interstitial values are interpolated accurately
interstitial_x_values.each do |x|
interstitial_y_values.each do |y|
expected_z = saddle(x,y)
z = i2d.eval(x,y)
error = (z - expected_z).abs
max_error = (expected_z.abs)*tolerance
if max_error == 0
max_error = tolerance
end
refute error > max_error, "error @ interstitial #{x},#{y}"
end
end
end
end if GSL::GSL_VERSION >= '2.0'
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