chisquare.go

   1 // Copyright (C) The Lightning Authors. All rights reserved.
   2 //
   3 // SPDX-License-Identifier: AGPL-3.0
   4
   5 package lightning
   6
   7 import (
   8         "gonum.org/v1/gonum/stat/distuv"
   9 )
  10
  11 var chisquared = distuv.ChiSquared{K: 1}
  12
  13 func pvalue(x, y []bool) float64 {
  14         var (
  15                 obs, exp [2]float64
  16                 sum      float64
  17                 sz       = float64(len(y))
  18         )
  19         for i, yi := range y {
  20                 if x[i] {
  21                         if yi {
  22                                 obs[0]++
  23                         } else {
  24                                 obs[1]++
  25                         }
  26                 }
  27                 if yi {
  28                         exp[0]++
  29                 } else {
  30                         exp[1]++
  31                 }
  32         }
  33         if exp[0] == 0 || exp[1] == 0 || obs[0]+obs[1] == 0 {
  34                 return 1
  35         }
  36         exp[0] = (obs[0] + obs[1]) * exp[0] / sz
  37         exp[1] = (obs[0] + obs[1]) * exp[1] / sz
  38         for i := range exp {
  39                 d := obs[i] - exp[i]
  40                 sum += d * d / exp[i]
  41         }
  42         return chisquared.Survival(sum)
  43 }