fixed dependencies

vendor/gonum.org/v1/gonum/stat/distuv/bernoulli.go

@@ -0,0 +1,141 @@
+// Copyright ©2016 The Gonum Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package distuv
+
+import (
+	"math"
+
+	"golang.org/x/exp/rand"
+)
+
+// Bernoulli represents a random variable whose value is 1 with probability p and
+// value of zero with probability 1-P. The value of P must be between 0 and 1.
+// More information at https://en.wikipedia.org/wiki/Bernoulli_distribution.
+type Bernoulli struct {
+	P   float64
+	Src rand.Source
+}
+
+// CDF computes the value of the cumulative density function at x.
+func (b Bernoulli) CDF(x float64) float64 {
+	if x < 0 {
+		return 0
+	}
+	if x < 1 {
+		return 1 - b.P
+	}
+	return 1
+}
+
+// Entropy returns the entropy of the distribution.
+func (b Bernoulli) Entropy() float64 {
+	if b.P == 0 || b.P == 1 {
+		return 0
+	}
+	q := 1 - b.P
+	return -b.P*math.Log(b.P) - q*math.Log(q)
+}
+
+// ExKurtosis returns the excess kurtosis of the distribution.
+func (b Bernoulli) ExKurtosis() float64 {
+	pq := b.P * (1 - b.P)
+	return (1 - 6*pq) / pq
+}
+
+// LogProb computes the natural logarithm of the value of the probability density function at x.
+func (b Bernoulli) LogProb(x float64) float64 {
+	if x == 0 {
+		return math.Log(1 - b.P)
+	}
+	if x == 1 {
+		return math.Log(b.P)
+	}
+	return math.Inf(-1)
+}
+
+// Mean returns the mean of the probability distribution.
+func (b Bernoulli) Mean() float64 {
+	return b.P
+}
+
+// Median returns the median of the probability distribution.
+func (b Bernoulli) Median() float64 {
+	p := b.P
+	switch {
+	case p < 0.5:
+		return 0
+	case p > 0.5:
+		return 1
+	default:
+		return 0.5
+	}
+}
+
+// NumParameters returns the number of parameters in the distribution.
+func (Bernoulli) NumParameters() int {
+	return 1
+}
+
+// Prob computes the value of the probability distribution at x.
+func (b Bernoulli) Prob(x float64) float64 {
+	if x == 0 {
+		return 1 - b.P
+	}
+	if x == 1 {
+		return b.P
+	}
+	return 0
+}
+
+// Quantile returns the minimum value of x from amongst all those values whose CDF value exceeds or equals p.
+func (b Bernoulli) Quantile(p float64) float64 {
+	if p < 0 || 1 < p {
+		panic(badPercentile)
+	}
+	if p <= 1-b.P {
+		return 0
+	}
+	return 1
+}
+
+// Rand returns a random sample drawn from the distribution.
+func (b Bernoulli) Rand() float64 {
+	var rnd float64
+	if b.Src == nil {
+		rnd = rand.Float64()
+	} else {
+		rnd = rand.New(b.Src).Float64()
+	}
+	if rnd < b.P {
+		return 1
+	}
+	return 0
+}
+
+// Skewness returns the skewness of the distribution.
+func (b Bernoulli) Skewness() float64 {
+	return (1 - 2*b.P) / math.Sqrt(b.P*(1-b.P))
+}
+
+// StdDev returns the standard deviation of the probability distribution.
+func (b Bernoulli) StdDev() float64 {
+	return math.Sqrt(b.Variance())
+}
+
+// Survival returns the survival function (complementary CDF) at x.
+func (b Bernoulli) Survival(x float64) float64 {
+	if x < 0 {
+		return 1
+	}
+	if x < 1 {
+		return b.P
+	}
+	return 0
+}
+
+// Variance returns the variance of the probability distribution.
+func (b Bernoulli) Variance() float64 {
+	return b.P * (1 - b.P)
+}