stat_npb.go

package stat

import (
	. "github.com/ematvey/go-fn/fn"
)

func CRP_PMF(α float64) func(x []int64) float64 {
	return func(x []int64) float64 {
		n := int64(len(x))
		counts := make([]int64, int(α*log(float64(len(x)))))
		sum := fZero

		p := fOne

		for i := iZero; i < n; i++ {
			if x[i] >= int64(len(counts)) {
				counts = copyInt64(counts, 2*int64(len(counts)))
			}

			if counts[x[i]] == 0 {
				p *= α / (sum + α)
			} else {
				p *= float64(x[i]) / (sum + α)
			}

			counts[x[i]] += 1
			sum += 1
		}
		return p
	}
}

func CRP_LnPMF(α float64) func(x []int64) float64 {
	return func(x []int64) float64 {
		counts := make([]float64, len(x))
		total := fZero
		r := fZero
		for _, c := range x {
			if counts[c] == 0 {
				r++
			}
			counts[c]++
			total++
		}
		ll := r * log(α)
		ll += LnΓ(α) - LnΓ(α+total)
		for _, count := range counts {
			if count != 0 {
				ll += LnΓ(count)
			}
		}
		return ll
	}
}

/*
func CRP_LnPMF2(α float64) func(x []int64) float64 {
	return func(x []int64) float64 {
		n := int64(len(x));
		counts := make([]int64, int(α*log(float64(len(x)))));
		sum := fZero;

		p := fZero;

		for i:=iZero; i<n; i++ {
			if x[i] >= int64(len(counts)) {
				counts = copyInt64(counts, 2*int64(len(counts)))
			}

			if counts[x[i]] == 0 {
				p += log(α)-log(sum+α);
			} else {
				p += log(float64(x[i]))-log(sum+α);
			}

			counts[x[i]] += 1;
			sum += 1;
		}
		return p;
	}
}
*/