adding timeseries example.

examples/timeseries/main.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/wcharczuk/go-chart"
+)
+
+func drawChart(res http.ResponseWriter, req *http.Request) {
+	/*
+	   This is an example of using the `TimeSeries` to automatically coerce time.Time values into a continuous xrange.
+	   Note: chart.TimeSeries implements `ValueFormatterProvider` and as a result gives the XAxis the appropariate formatter to use for the ticks.
+	*/
+	graph := chart.Chart{
+		XAxis: chart.XAxis{
+			Style: chart.Style{
+				Show: true,
+			},
+		},
+		Series: []chart.Series{
+			chart.TimeSeries{
+				XValues: []time.Time{
+					time.Now().AddDate(0, 0, -10),
+					time.Now().AddDate(0, 0, -9),
+					time.Now().AddDate(0, 0, -8),
+					time.Now().AddDate(0, 0, -7),
+					time.Now().AddDate(0, 0, -6),
+					time.Now().AddDate(0, 0, -5),
+					time.Now().AddDate(0, 0, -4),
+					time.Now().AddDate(0, 0, -3),
+					time.Now().AddDate(0, 0, -2),
+					time.Now().AddDate(0, 0, -1),
+					time.Now(),
+				},
+				YValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0},
+			},
+		},
+	}
+
+	res.Header().Set("Content-Type", "image/png")
+	graph.Render(chart.PNG, res)
+}
+
+func main() {
+	http.HandleFunc("/", drawChart)
+	http.ListenAndServe(":8080", nil)
+}

util.go

@@ -156,6 +156,15 @@ func SeqRand(samples int, scale float64) []float64 {
 	return values
 }
 
+// SeqDays generates a sequence of timestamps by day, from -days to today.
+func SeqDays(days int) []time.Time {
+	var values []time.Time
+	for day := days; day >= 0; day-- {
+		values = append(values, time.Now().AddDate(0, 0, -day))
+	}
+	return values
+}
+
 // PercentDifference computes the percentage difference between two values.
 // The formula is (v2-v1)/v1.
 func PercentDifference(v1, v2 float64) float64 {