calculate Y Axis scale for multi-timeseries plot

tsplot/plot.go

@@ -56,6 +56,7 @@ func findMaxFromInt64Data(points []*monitoringpb.Point) float64 {
 	return float64(maximum)
 }
 
+// NewPlotFromTimeSeries creates a plot from a single time series.
 func NewPlotFromTimeSeries(ts *monitoringpb.TimeSeries, opts ...PlotOption) (*plot.Plot, error) {
 	points := ts.GetPoints()
 	YMax, err := findMaxFromPoints(ts.GetValueType(), points)
@@ -73,7 +74,10 @@ func NewPlotFromTimeSeries(ts *monitoringpb.TimeSeries, opts ...PlotOption) (*pl
 	return p, nil
 }
 
+// NewPlotFromTimeSeriesIterator creates a plot from multiple time series.
 func NewPlotFromTimeSeriesIterator(tsi *monitoring.TimeSeriesIterator, legendKey string, opts ...PlotOption) (*plot.Plot, error) {
+
+	var yMax float64
 	p := plot.New()
 	for {
 		timeSeries, err := tsi.Next()
@@ -84,6 +88,15 @@ func NewPlotFromTimeSeriesIterator(tsi *monitoring.TimeSeriesIterator, legendKey
 			return nil, err
 		}
 
+		points := timeSeries.GetPoints()
+
+		// Find the maximum datapoint between the different time series data.
+		// Use this to scale the Y Axis.
+		curMax, _ := findMaxFromPoints(points)
+		if curMax > yMax {
+			yMax = curMax
+		}
+
 		// add colored line to plot
 		lineColor := getUnusedColor()
 		applyLine := WithColoredLineFromPoints(timeSeries.GetPoints(), lineColor)
@@ -94,7 +107,7 @@ func NewPlotFromTimeSeriesIterator(tsi *monitoring.TimeSeriesIterator, legendKey
 		legendEntry.Color = lineColor
 		p.Legend.Add(timeSeries.GetMetric().GetLabels()[legendKey], legendEntry)
 
-		p.Y.Max = 400 // todo: make dynamic according to data
+		p.Y.Max = yMax + 200
 	}
 
 	for _, opt := range opts {