benfords-law/main.go
2020-11-14 20:12:11 -07:00

68 lines
2.5 KiB
Go

package main
import (
"bufio"
"fmt"
"log"
"math"
"math/rand"
"os"
"time"
)
const (
randomMin = 1 // We specify a range which random numbers will be generated, we must start at the first possible left-most digit
randomMax = 999999999999999999 // int64 max value is 9223372036854775807. We use one digit less than that with all 9's in order to not give bias to any digits.
numSamples = 100000000 // A nice rounded human number
)
func main() {
// In results, we store a count of each left most leading digits as numbers are randomly genereated
results := [9]int{} // There are 9 possible leading digits and 0 does not count, offset by 1 for index to actual value. Examples: To access count for 1 use [0]. To access 5 use [4]. To access 9 use [8].
currentSample := 0 // A counter that increments each time a random number sample has been generated. Used for status messages
// Start a little goroutine to output status and attach a ticker to execute it each second
statusTicker := time.NewTicker(time.Second)
go func() {
for {
<-statusTicker.C // Wait for heartbeat from ticker channel
percentCompleted := (currentSample * 100) / numSamples
log.Printf("%d%% completed generating and analyzing samples", percentCompleted)
}
}()
log.Printf("generating numbers...")
rand.Seed(time.Now().UnixNano())
for currentSample = 0; currentSample < numSamples; currentSample++ {
results[firstDigit(rand.Intn(randomMax-randomMin+1)+randomMin)-1]++ // Generate a random number between randomMin and randomMax, get the first digit then increment the counter in results array, remember, it's offset by 1
}
// Done generating and counting digits, stop the status ticker
statusTicker.Stop()
log.Printf("done.")
// Output results
for digitMinusOne, digitCount := range results {
fmt.Printf("%d: %d (%f%%)\n", digitMinusOne+1, digitCount, float64(digitCount*100)/float64(numSamples))
}
// Wait indefinitely until Enter Key is pressed, avoid terminating terminal before viewing results if ran from a shell
fmt.Print("Press 'Enter' to continue...")
bufio.NewReader(os.Stdin).ReadBytes('\n')
}
// firstDigit returns the first/leftmost digit of the base10 representation of an integer
func firstDigit(x int) int {
return int(math.Abs(float64(x)) / math.Pow(10, float64(numDigits(x)-1)))
}
// numDigits returns the number of digits
func numDigits(x int) int {
if x == 0 {
return 1
}
return int(math.Floor(math.Log10(math.Abs(float64(x))))) + 1
}