started to add a histogram on key.

stats.go

@@ -11,10 +11,55 @@ const initialLength int = 1024
 const verySmall float64 = -100000
 const veryBig float64 = 100000
 
+type Histogram struct {
+	Min      float64 `json:"min"`
+	StepSize float64 `json:"step_size"`
+	Values   []int   `json:"values"`
+}
+
 type Stats struct {
 	Mean float64 `json:"mean"`
 	Var  float64 `json:"var"`
 	Std  float64 `json:"std"`
+	Min  float64 `json:"min"`
+	Max  float64 `json:"max"`
+	N    int     `json:"n"`
+}
+
+func (this *Stats) findMinHistogramValue() float64 {
+	return math.Max(this.Min, this.Mean-3*this.Std)
+}
+
+func (this *Stats) findMaxHistogramValue() float64 {
+	return math.Min(this.Max, this.Mean+3*this.Std)
+}
+
+func (this *Stats) findSuitableBinForDatum(min, step, val float64) int {
+	var i int
+	var act float64 = min
+	for i = 0; act < val; act += step {
+		i++
+	}
+	return i - 1
+
+}
+
+func (this *Stats) MakeHistogram(numberOfBins int, dataChannel chan float64, outputChannel chan *Histogram) {
+	min := this.findMinHistogramValue()
+	max := this.findMaxHistogramValue()
+	step := (max - min) / float64(numberOfBins)
+	hist := make([]int, numberOfBins)
+
+	for datum := range dataChannel {
+		if datum < min || datum > max {
+			continue
+		}
+		i := this.findSuitableBinForDatum(min, step, datum)
+		hist[i]++
+	}
+
+	outputChannel <- &Histogram{min, step, hist}
+
 }
 
 type StatAggregator struct {
@@ -50,7 +95,9 @@ func (this *StatAggregator) getFinalStats() *Stats {
 	stats.Mean = this.sum / float64(this.n)
 	stats.Var = this.sumOfTheSquares/float64(this.n) - stats.Mean*stats.Mean
 	stats.Std = math.Sqrt(stats.Var)
+	stats.Min = this.min
+	stats.Max = this.max
+	stats.N = this.n
 
 	return stats
-
 }