math.go

package main

import (
	"math"
	"sort"
)

func maxFrequency(buckets [][]float64) float64 {
	var max float64

	for _, b := range buckets {
		n := float64(len(b))
		if n > max {
			max = n
		}
	}

	return max
}

func maxInt(values []int) int {
	max := math.MinInt64
	for _, v := range values {
		if v > max {
			max = v
		}
	}

	return max
}

func maxFloat64(values []float64) float64 {
	max := -math.MaxFloat64
	for _, v := range values {
		max = math.Max(max, v)
	}

	return max
}

func minFloat64(values []float64) float64 {
	min := math.MaxFloat64
	for _, v := range values {
		min = math.Min(min, v)
	}

	return min
}

func avgFloat64(fs []float64) float64 {
	var sum float64
	for _, f := range fs {
		sum += f
	}

	return sum / float64(len(fs))
}

func categories(buckets []bucket) []string {
	keys := make([]string, len(buckets))
	for i, b := range buckets {
		keys[i] = b.Category
	}

	return keys
}

func frequencies(buckets []bucket) []int {
	values := make([]int, len(buckets))
	for i, b := range buckets {
		values[i] = b.Frequency
	}

	return values
}

func frequenciesFloat64(buckets []bucket) []float64 {
	values := make([]float64, len(buckets))
	for i, b := range buckets {
		values[i] = float64(b.Frequency)
	}

	return values
}

func percentile(p float64, values []float64) float64 {
	samples := make([]float64, len(values))
	copy(samples, values)

	sort.Float64s(samples)

	val := p * float64(len(samples))
	index := int(math.Ceil(val))

	return samples[index-1]
}