40 lines
979 B
Go
40 lines
979 B
Go
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// Copyright (c) 2012, Matt T. Proud
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// All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// distributions.go provides basic distribution-generating functions that are
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// used primarily in testing contexts.
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package maths
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import (
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"math"
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)
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// Go's standard library does not offer a factorial function.
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func Factorial(of int) int64 {
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if of <= 0 {
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return 1
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}
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var result int64 = 1
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for i := int64(of); i >= 1; i-- {
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result *= i
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}
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return result
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}
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// Create calculate the value of a probability density for a given binomial
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// statistic, where k is the target count of true cases, n is the number of
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// subjects, and p is the probability.
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func BinomialPDF(k, n int, p float64) float64 {
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binomialCoefficient := float64(Factorial(n)) / float64(Factorial(k)*Factorial(n-k))
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intermediate := math.Pow(p, float64(k)) * math.Pow(1-p, float64(n-k))
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return binomialCoefficient * intermediate
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}
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