Adding upstream version 2.1.2.

Signed-off-by: Daniel Baumann <daniel@debian.org>

logarithmic_range.go

@@ -0,0 +1,94 @@
+package chart
+
+import (
+	"fmt"
+	"math"
+)
+
+// LogarithmicRange represents a boundary for a set of numbers.
+type LogarithmicRange struct {
+	Min        float64
+	Max        float64
+	Domain     int
+	Descending bool
+}
+
+// IsDescending returns if the range is descending.
+func (r LogarithmicRange) IsDescending() bool {
+	return r.Descending
+}
+
+// IsZero returns if the LogarithmicRange has been set or not.
+func (r LogarithmicRange) IsZero() bool {
+	return (r.Min == 0 || math.IsNaN(r.Min)) &&
+		(r.Max == 0 || math.IsNaN(r.Max)) &&
+		r.Domain == 0
+}
+
+// GetMin gets the min value for the continuous range.
+func (r LogarithmicRange) GetMin() float64 {
+	return r.Min
+}
+
+// SetMin sets the min value for the continuous range.
+func (r *LogarithmicRange) SetMin(min float64) {
+	r.Min = min
+}
+
+// GetMax returns the max value for the continuous range.
+func (r LogarithmicRange) GetMax() float64 {
+	return r.Max
+}
+
+// SetMax sets the max value for the continuous range.
+func (r *LogarithmicRange) SetMax(max float64) {
+	r.Max = max
+}
+
+// GetDelta returns the difference between the min and max value.
+func (r LogarithmicRange) GetDelta() float64 {
+	return r.Max - r.Min
+}
+
+// GetDomain returns the range domain.
+func (r LogarithmicRange) GetDomain() int {
+	return r.Domain
+}
+
+// SetDomain sets the range domain.
+func (r *LogarithmicRange) SetDomain(domain int) {
+	r.Domain = domain
+}
+
+// String returns a simple string for the LogarithmicRange.
+func (r LogarithmicRange) String() string {
+	return fmt.Sprintf("LogarithmicRange [%.2f,%.2f] => %d", r.Min, r.Max, r.Domain)
+}
+
+// Translate maps a given value into the LogarithmicRange space. Modified version from ContinuousRange.
+func (r LogarithmicRange) Translate(value float64) int {
+	if value < 1 {
+		return 0
+	}
+	normalized := math.Max(value-r.Min, 1)
+	ratio := math.Log10(normalized) / math.Log10(r.GetDelta())
+
+	if r.IsDescending() {
+		return r.Domain - int(math.Ceil(ratio*float64(r.Domain)))
+	}
+
+	return int(math.Ceil(ratio * float64(r.Domain)))
+}
+
+// GetTicks calculates the needed ticks for the axis, in log scale. Only supports Y values > 0.
+func (r LogarithmicRange) GetTicks(render Renderer, defaults Style, vf ValueFormatter) []Tick {
+	var ticks []Tick
+	exponentStart := int64(math.Max(0, math.Floor(math.Log10(r.Min))))   // one below min
+	exponentEnd := int64(math.Max(0, math.Ceil(math.Log10(r.Max))))      // one above max
+	for exp:=exponentStart; exp<=exponentEnd; exp++ {
+		tickVal := math.Pow(10, float64(exp))
+		ticks = append(ticks, Tick{Value: tickVal, Label: vf(tickVal)})
+	}
+
+	return ticks
+}