route/vendor/github.com/aclements/go-moremath/stats/deltadist.go

58 lines
1.0 KiB
Go

// Copyright 2015 The Go 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 stats
// DeltaDist is the Dirac delta function, centered at T, with total
// area 1.
//
// The CDF of the Dirac delta function is the Heaviside step function,
// centered at T. Specifically, f(T) == 1.
type DeltaDist struct {
T float64
}
func (d DeltaDist) PDF(x float64) float64 {
if x == d.T {
return inf
}
return 0
}
func (d DeltaDist) pdfEach(xs []float64) []float64 {
res := make([]float64, len(xs))
for i, x := range xs {
if x == d.T {
res[i] = inf
}
}
return res
}
func (d DeltaDist) CDF(x float64) float64 {
if x >= d.T {
return 1
}
return 0
}
func (d DeltaDist) cdfEach(xs []float64) []float64 {
res := make([]float64, len(xs))
for i, x := range xs {
res[i] = d.CDF(x)
}
return res
}
func (d DeltaDist) InvCDF(y float64) float64 {
if y < 0 || y > 1 {
return nan
}
return d.T
}
func (d DeltaDist) Bounds() (float64, float64) {
return d.T - 1, d.T + 1
}