Function ExamplePolygon_hexagons

plotter/polygon_example_test.go:84–146

ExamplePolygon_hexagons creates a heat map with hexagon shapes. The output of this example is at https://github.com/gonum/plot/blob/master/plotter/testdata/polygon_hexagons_golden.png.

()

// The output of this example is at
// https://github.com/gonum/plot/blob/master/plotter/testdata/polygon_hexagons_golden.png.
func ExamplePolygon_hexagons() {
	// hex returns a hexagon centered at (x,y) with radius r.
	hex := func(x, y, r float64) plotter.XYs {
		g := make(plotter.XYs, 6)
		for i := range g {
			g[i].X = x + r*math.Cos(math.Pi/3*float64(i))
			g[i].Y = y + r*math.Sin(math.Pi/3*float64(i))
		}
		return g
	}

	var err error
	p := plot.New()
	p.Title.Text = "Hexagons"
	p.X.Label.Text = "X"
	p.Y.Label.Text = "Y"

	colorMap := moreland.SmoothBlueRed()
	colorMap.SetMax(2)
	colorMap.SetMin(-2)
	colorMap.SetConvergePoint(0)

	const (
		r = math.Pi / 4 // r is the hexagon radius.
		// x0 and y0 are the beginning coordinates for the hexagon plot.
		x0 = 0.0
		y0 = 0.0
		// nx and ny are the number of hexagons in the x and y directions.
		nx = 5
		ny = 5
	)
	// dx and dy are the distance between hexgons.
	dx := 3 * r
	dy := r * math.Sqrt(3)

	xstart := []float64{x0, x0 - 1.5*r}
	ystart := []float64{y0, y0 - r}
	for i, xmin := range xstart {
		ymin := ystart[i]
		x := xmin
		for range nx {
			y := ymin
			for range ny {
				var poly *plotter.Polygon
				poly, err = plotter.NewPolygon(hex(x, y, r))
				if err != nil {
					log.Panic(err)
				}
				poly.Color, err = colorMap.At(math.Sin(x) + math.Sin(y))
				if err != nil {
					log.Panic(err)
				}
				poly.LineStyle.Width = 0
				p.Add(poly)
				y += dy
			}
			x += dx
		}