benfords-law/main.go

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package main
import (
"bufio"
"fmt"
"log"
"math"
"math/rand"
"os"
"time"
)
const (
randomMin = 0
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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
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)
func main() {
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 1 use [0]. To access 5 use [4]. To access 9 use [8].
currentSample := 0
statusTicker := time.NewTicker(time.Second)
go func() {
for {
<-statusTicker.C
percentCompleted := (currentSample * 100) / numSamples
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log.Printf("%d%% completed generating and analyzing samples", percentCompleted)
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}
}()
log.Printf("generating numbers...")
rand.Seed(time.Now().UnixNano())
for currentSample = 0; currentSample < numSamples; currentSample++ {
results[firstDigit(rand.Intn(randomMax-randomMin+1)+randomMin)-1]++ // We must use Intn instead of Int because from Base10's perspective, integers cut off at a really weird spot
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}
statusTicker.Stop()
log.Printf("done.")
// output results
for digitMinusOne, count := range results {
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fmt.Printf("%d: %d (%f%%)\n", digitMinusOne+1, count, float64(count*100)/float64(numSamples))
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}
fmt.Print("Press 'Enter' to continue...")
bufio.NewReader(os.Stdin).ReadBytes('\n')
}
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// firstDigit returns the first/leftmost digit of the base10 representation of an integer
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func firstDigit(x int) int {
return int(math.Abs(float64(x)) / math.Pow(10, float64(numDigits(x)-1)))
}
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// numDigits returns the number of digits
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func numDigits(x int) int {
if x == 0 {
return 1
}
return int(math.Floor(math.Log10(math.Abs(float64(x))))) + 1
}