introduces the Range interface (instead of a concrete type).

continuous_range_test.go

@@ -0,0 +1,22 @@
+package chart
+
+import (
+	"testing"
+
+	"github.com/blendlabs/go-assert"
+)
+
+func TestRangeTranslate(t *testing.T) {
+	assert := assert.New(t)
+	values := []float64{1.0, 2.0, 2.5, 2.7, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0}
+	r := ContinuousRange{Domain: 1000}
+	r.Min, r.Max = MinAndMax(values...)
+
+	// delta = ~7.0
+	// value = ~5.0
+	// domain = ~1000
+	// 5/8 * 1000 ~=
+	assert.Equal(0, r.Translate(1.0))
+	assert.Equal(1000, r.Translate(8.0))
+	assert.Equal(572, r.Translate(5.0))
+}