Adding upstream version 2.1.2.

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

examples/custom_formatters/main.go

@@ -0,0 +1,38 @@
+package main
+
+//go:generate go run main.go
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/wcharczuk/go-chart/v2"
+)
+
+func main() {
+	/*
+	   In this example we use a custom `ValueFormatter` for the y axis, letting us specify how to format text of the y-axis ticks.
+	   You can also do this for the x-axis, or the secondary y-axis.
+	   This example also shows what the chart looks like with the x-axis left off or not shown.
+	*/
+
+	graph := chart.Chart{
+		YAxis: chart.YAxis{
+			ValueFormatter: func(v interface{}) string {
+				if vf, isFloat := v.(float64); isFloat {
+					return fmt.Sprintf("%0.6f", vf)
+				}
+				return ""
+			},
+		},
+		Series: []chart.Series{
+			chart.ContinuousSeries{
+				XValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
+				YValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
+			},
+		},
+	}
+	f, _ := os.Create("output.png")
+	defer f.Close()
+	graph.Render(chart.PNG, f)
+}