Function ExampleBarChart_positiveNegative

plotter/barchart_example_test.go:159–249

This example shows a bar chart with both positive and negative values.

()

// This example shows a bar chart with both positive and negative values.
func ExampleBarChart_positiveNegative() {
	rnd := rand.New(rand.NewPCG(1, 1))

	// Create random data points between -1 and 1.
	const n = 6
	data1 := make(plotter.Values, n)
	data2 := make(plotter.Values, n)
	net := make(plotter.XYs, n) // net = data1 + data2
	for i := range n {
		data1[i] = rnd.Float64()*2 - 1
		data2[i] = rnd.Float64()*2 - 1
		net[i].X = data1[i] + data2[i]
		net[i].Y = float64(i)
	}

	// splitBySign splits an array into two arrays containing the positive and
	// negative values, respectively, from the original array.
	splitBySign := func(d plotter.Values) (pos, neg plotter.Values) {
		pos = make(plotter.Values, len(d))
		neg = make(plotter.Values, len(d))
		for i, v := range d {
			if v > 0 {
				pos[i] = v
			} else {
				neg[i] = v
			}
		}
		return
	}

	data1Pos, data1Neg := splitBySign(data1)
	data2Pos, data2Neg := splitBySign(data2)

	const barWidth = 0.3 * vg.Centimeter
	pos1, err := plotter.NewBarChart(data1Pos, barWidth)
	if err != nil {
		log.Panic(err)
	}
	pos2, err := plotter.NewBarChart(data2Pos, barWidth)
	if err != nil {
		log.Panic(err)
	}
	neg1, err := plotter.NewBarChart(data1Neg, barWidth)
	if err != nil {
		log.Panic(err)
	}
	neg2, err := plotter.NewBarChart(data2Neg, barWidth)
	if err != nil {
		log.Panic(err)
	}

	netDots, err := plotter.NewScatter(net)
	if err != nil {
		log.Panic(err)
	}
	netDots.Radius = vg.Points(1.25)

	pos2.StackOn(pos1) // Specify that pos2 goes on top of pos1.