Function ExampleScatter_color

plotter/scatterColor_example_test.go:25–128

ExampleScatter_color draws a colored scatter plot. Each point is plotted with a different color depending on external criteria.

()

// Each point is plotted with a different color depending on
// external criteria.
func ExampleScatter_color() {
	rnd := rand.New(rand.NewPCG(1, 1))

	// randomTriples returns some random but correlated x, y, z triples
	randomTriples := func(n int) plotter.XYZs {
		data := make(plotter.XYZs, n)
		for i := range data {
			if i == 0 {
				data[i].X = rnd.Float64()
			} else {
				data[i].X = data[i-1].X + 2*rnd.Float64()
			}
			data[i].Y = data[i].X + 10*rnd.Float64()
			data[i].Z = data[i].X
		}
		return data
	}

	n := 15
	scatterData := randomTriples(n)

	// Calculate the range of Z values.
	minZ, maxZ := math.Inf(1), math.Inf(-1)
	for _, xyz := range scatterData {
		if xyz.Z > maxZ {
			maxZ = xyz.Z
		}
		if xyz.Z < minZ {
			minZ = xyz.Z
		}
	}

	colors := moreland.Kindlmann() // Initialize a color map.
	colors.SetMax(maxZ)
	colors.SetMin(minZ)

	p := plot.New()
	p.Title.Text = "Colored Points Example"
	p.X.Label.Text = "X"
	p.Y.Label.Text = "Y"
	p.Add(plotter.NewGrid())

	sc, err := plotter.NewScatter(scatterData)
	if err != nil {
		log.Panic(err)
	}

	// Specify style and color for individual points.
	sc.GlyphStyleFunc = func(i int) draw.GlyphStyle {
		_, _, z := scatterData.XYZ(i)
		d := (z - minZ) / (maxZ - minZ)
		rng := maxZ - minZ
		k := d*rng + minZ
		// Clamp k to avoid potential overflow due to floating point error.
		c, err := colors.At(min(k, colors.Max()))
		if err != nil {
			log.Panic(err)
		}