32 lines
673 B
Ruby
32 lines
673 B
Ruby
class RandomGaussian
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def initialize(mean, stddev, rand_helper = lambda { Kernel.rand })
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@rand_helper = rand_helper
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@mean = mean
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@stddev = stddev
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@valid = false
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@next = 0
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end
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def rand
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if @valid then
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@valid = false
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return @next
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else
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@valid = true
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x, y = self.class.gaussian(@mean, @stddev, @rand_helper)
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@next = y
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return x
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end
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end
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private
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def self.gaussian(mean, stddev, rand)
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theta = 2 * Math::PI * rand.call
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rho = Math.sqrt(-2 * Math.log(1 - rand.call))
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scale = stddev * rho
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x = mean + scale * Math.cos(theta)
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y = mean + scale * Math.sin(theta)
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return x, y
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end
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end
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