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module Distribution
module Weibull
module Ruby_
class << self
def pdf(x, k, lam)
return 0.0 if x < 0.0
return ((k.to_f/lam.to_f)*(x.to_f/lam.to_f)**(k-1.0))*Math.exp(-(x.to_f/lam.to_f)**k)
end
#Returns the integral of the Weibull distribution from [-Inf to x]
def cdf(x, k, lam)
return 0.0 if x < 0.0
return 1.0-Math.exp(-(x.to_f/lam.to_f)**k)
end
# Returns the P-value of weibull
def p_value(y, k, lam)
return 1.0 if y > 1.0
return 0.0 if y < 0.0
return -lam*(Math.log(1.0-y))**(1.0/k)
end
end
end
end
end
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