Data commit

Task/Statistics-Basic/Go/statistics-basic-1.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+    "fmt"
+    "math"
+    "math/rand"
+    "strings"
+)
+
+func main() {
+    sample(100)
+    sample(1000)
+    sample(10000)
+}
+
+func sample(n int) {
+    // generate data
+    d := make([]float64, n)
+    for i := range d {
+        d[i] = rand.Float64()
+    }
+    // show mean, standard deviation
+    var sum, ssq float64
+    for _, s := range d {
+        sum += s
+        ssq += s * s
+    }
+    fmt.Println(n, "numbers")
+    m := sum / float64(n)
+    fmt.Println("Mean:  ", m)
+    fmt.Println("Stddev:", math.Sqrt(ssq/float64(n)-m*m))
+    // show histogram
+    h := make([]int, 10)
+    for _, s := range d {
+        h[int(s*10)]++
+    }
+    for _, c := range h {
+        fmt.Println(strings.Repeat("*", c*205/int(n)))
+    }
+    fmt.Println()
+}

Task/Statistics-Basic/Go/statistics-basic-2.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+    "fmt"
+    "math"
+    "math/rand"
+    "strings"
+)
+
+func main() {
+    bigSample(1e7)
+}
+
+func bigSample(n int64) {
+    sum, ssq, h := reduce(0, n)
+    // compute final statistics and output as above
+    fmt.Println(n, "numbers")
+    m := sum / float64(n)
+    fmt.Println("Mean:  ", m)
+    fmt.Println("Stddev:", math.Sqrt(ssq/float64(n)-m*m))
+    for _, c := range h {
+        fmt.Println(strings.Repeat("*", c*205/int(n)))
+    }
+    fmt.Println()
+}
+
+const threshold = 1e6
+
+func reduce(start, end int64) (sum, ssq float64, h []int) {
+    n := end - start
+    if n < threshold {
+        d := getSegment(start, end)
+        return computeSegment(d)
+    }
+    // map to two sub problems
+    half := (start + end) / 2
+    sum1, ssq1, h1 := reduce(start, half)
+    sum2, ssq2, h2 := reduce(half, end)
+    // combine results
+    for i, c := range h2 {
+        h1[i] += c
+    }
+    return sum1 + sum2, ssq1 + ssq2, h1
+}
+
+func getSegment(start, end int64) []float64 {
+    d := make([]float64, end-start)
+    for i := range d {
+        d[i] = rand.Float64()
+    }
+    return d
+}
+
+func computeSegment(d []float64) (sum, ssq float64, h []int) {
+    for _, s := range d {
+        sum += s
+        ssq += s * s
+    }
+    h = make([]int, 10)
+    for _, s := range d {
+        h[int(s*10)]++
+    }
+    return
+}