all: modernize Go usage

align.go

@@ -25,13 +25,13 @@ func Align(plots [][]*Plot, t draw.Tiles, dc draw.Canvas) [][]draw.Canvas {
 	}
 
 	// Create the initial tiles.
-	for j := 0; j < t.Rows; j++ {
+	for j := range t.Rows {
 		if len(plots[j]) != t.Cols {
 			panic(fmt.Errorf("plot: plots row %d columns (%d) != tiles columns (%d)", j, len(plots[j]), t.Rows))
 		}
 
 		o[j] = make([]draw.Canvas, len(plots[j]))
-		for i := 0; i < t.Cols; i++ {
+		for i := range t.Cols {
 			o[j][i] = t.At(dc, i, j)
 		}
 	}

align_example_test.go

@@ -18,9 +18,9 @@ import (
 func ExampleAlign() {
 	const rows, cols = 4, 3
 	plots := make([][]*plot.Plot, rows)
-	for j := 0; j < rows; j++ {
+	for j := range rows {
 		plots[j] = make([]*plot.Plot, cols)
-		for i := 0; i < cols; i++ {
+		for i := range cols {
 			if i == 0 && j == 2 {
 				// This shows what happens when there are nil plots.
 				continue
@@ -70,8 +70,8 @@ func ExampleAlign() {
 	}
 
 	canvases := plot.Align(plots, t, dc)
-	for j := 0; j < rows; j++ {
-		for i := 0; i < cols; i++ {
+	for j := range rows {
+		for i := range cols {
 			if plots[j][i] != nil {
 				plots[j][i].Draw(canvases[j][i])
 			}

palette/brewer/brewer.go

@@ -125,7 +125,7 @@ func GetPalette(typ PaletteType, name string, colors int) (palette.Palette, erro
 	)
 	switch typ {
 	case TypeAny:
-		var pt interface{}
+		var pt any
 		pt, nameOk = all[name]
 		if !nameOk {
 			break

palette/brewer/palettes.go

@@ -4752,7 +4752,7 @@ var (
 		"YlOrBr":  YlOrBr,
 		"YlOrRd":  YlOrRd,
 	}
-	all = map[string]interface{}{
+	all = map[string]any{
 		"BrBG":     BrBG,
 		"PiYG":     PiYG,
 		"PRGn":     PRGn,

palette/moreland/example_test.go

@@ -53,8 +53,8 @@ func Example() {
 		YOffset: -50,
 		Data:    mat.NewDense(100, 100, nil),
 	}
-	for i := 0; i < 100; i++ {
-		for j := 0; j < 100; j++ {
+	for i := range 100 {
+		for j := range 100 {
 			x := float64(i-50) / 10
 			y := float64(j-50) / 10
 			v := math.Sin(x*x+y*y) / (x*x + y*y)

palette/moreland/luminance.go

@@ -178,7 +178,7 @@ func (l luminance) Palette(n int) palette.Palette {
 	delta := (l.max - l.min) / float64(n-1)
 	var v float64
 	c := make([]color.Color, n)
-	for i := 0; i < n; i++ {
+	for i := range n {
 		v = l.min + float64(delta*float64(i))
 		var err error
 		c[i], err = l.At(v)

plotter/barchart_example_test.go

@@ -165,7 +165,7 @@ func ExampleBarChart_positiveNegative() {
 	data1 := make(plotter.Values, n)
 	data2 := make(plotter.Values, n)
 	net := make(plotter.XYs, n) // net = data1 + data2
-	for i := 0; i < n; i++ {
+	for i := range n {
 		data1[i] = rnd.Float64()*2 - 1
 		data2[i] = rnd.Float64()*2 - 1
 		net[i].X = data1[i] + data2[i]

plotter/boxplot_example_test.go

@@ -24,7 +24,7 @@ func ExampleBoxPlot() {
 	uniform := make(plotter.ValueLabels, n)
 	normal := make(plotter.ValueLabels, n)
 	expon := make(plotter.ValueLabels, n)
-	for i := 0; i < n; i++ {
+	for i := range n {
 		uniform[i].Value = rnd.Float64()
 		uniform[i].Label = fmt.Sprintf("%4.4f", uniform[i].Value)
 		normal[i].Value = rnd.NormFloat64()

plotter/colorbar.go

@@ -62,7 +62,7 @@ func (l *ColorBar) Plot(c draw.Canvas, p *plot.Plot) {
 			Min: image.Point{X: 0, Y: 0},
 			Max: image.Point{X: 1, Y: colors},
 		})
-		for i := 0; i < colors; i++ {
+		for i := range colors {
 			color, err := l.ColorMap.At(l.ColorMap.Min() + delta*float64(i))
 			if err != nil {
 				panic(err)
@@ -75,7 +75,7 @@ func (l *ColorBar) Plot(c draw.Canvas, p *plot.Plot) {
 			Min: image.Point{X: 0, Y: 0},
 			Max: image.Point{X: colors, Y: 1},
 		})
-		for i := 0; i < colors; i++ {
+		for i := range colors {
 			color, err := l.ColorMap.At(l.ColorMap.Min() + delta*float64(i))
 			if err != nil {
 				panic(err)

plotter/conrec.go

@@ -76,8 +76,8 @@ func conrec(g GridXYZ, heights []float64, fn conrecLine) {
 	)
 
 	c, r := g.Dims()
-	for i := 0; i < c-1; i++ {
-		for j := 0; j < r-1; j++ {
+	for i := range c - 1 {
+		for j := range r - 1 {
 			dmin := math.Min(
 				math.Min(g.Z(i, j), g.Z(i, j+1)),
 				math.Min(g.Z(i+1, j), g.Z(i+1, j+1)),
@@ -92,7 +92,7 @@ func conrec(g GridXYZ, heights []float64, fn conrecLine) {
 				continue
 			}
 
-			for k := 0; k < len(heights); k++ {
+			for k := range heights {
 				if heights[k] < dmin || dmax < heights[k] {
 					continue
 				}

plotter/contour.go

@@ -7,6 +7,7 @@ package plotter
 import (
 	"image/color"
 	"math"
+	"slices"
 	"sort"
 
 	"gonum.org/v1/plot"
@@ -64,8 +65,8 @@ func NewContour(g GridXYZ, levels []float64, p palette.Palette) *Contour {
 	default:
 		min, max = math.Inf(1), math.Inf(-1)
 		c, r := g.Dims()
-		for i := 0; i < c; i++ {
-			for j := 0; j < r; j++ {
+		for i := range c {
+			for j := range r {
 				v := g.Z(i, j)
 				if math.IsNaN(v) {
 					continue
@@ -98,8 +99,8 @@ var defaultQuantiles = []float64{0.01, 0.05, 0.25, 0.5, 0.75, 0.95, 0.99}
 func quantilesR7(g GridXYZ, p []float64) []float64 {
 	c, r := g.Dims()
 	data := make([]float64, 0, c*r)
-	for i := 0; i < c; i++ {
-		for j := 0; j < r; j++ {
+	for i := range c {
+		for j := range r {
 			if v := g.Z(i, j); !math.IsNaN(v) {
 				data = append(data, v)
 			}
@@ -267,8 +268,8 @@ func (h *Contour) DataRange() (xmin, xmax, ymin, ymax float64) {
 func (h *Contour) GlyphBoxes(plt *plot.Plot) []plot.GlyphBox {
 	c, r := h.GridXYZ.Dims()
 	b := make([]plot.GlyphBox, 0, r*c)
-	for i := 0; i < c; i++ {
-		for j := 0; j < r; j++ {
+	for i := range c {
+		for j := range r {
 			b = append(b, plot.GlyphBox{
 				X: plt.X.Norm(h.GridXYZ.X(i)),
 				Y: plt.Y.Norm(h.GridXYZ.Y(j)),
@@ -651,7 +652,7 @@ func (c *contour) exciseQuick(conts contourSet) {
 			conts[&contour{
 				z:        c.z,
 				backward: path{wp[i]},
-				forward:  append(path(nil), wp[i+1:j+1]...),
+				forward:  slices.Clone(wp[i+1 : j+1]),
 			}] = struct{}{}
 			wp = append(wp[:i], wp[j:]...)
 			j = i + 1

plotter/contour_test.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"math"
 	"reflect"
+	"slices"
 	"sort"
 	"testing"
 
@@ -457,8 +458,8 @@ func TestExciseLoops(t *testing.T) {
 		for i, test := range loopTests {
 			gotSet := make(contourSet)
 			c := &contour{
-				backward: append(path(nil), test.c.backward...),
-				forward:  append(path(nil), test.c.forward...),
+				backward: slices.Clone(test.c.backward),
+				forward:  slices.Clone(test.c.forward),
 			}
 			gotSet[c] = struct{}{}
 			c.exciseLoops(gotSet, quick)

plotter/field.go

@@ -66,8 +66,8 @@ type Field struct {
 func NewField(f FieldXY) *Field {
 	max := math.Inf(-1)
 	c, r := f.Dims()
-	for i := 0; i < c; i++ {
-		for j := 0; j < r; j++ {
+	for i := range c {
+		for j := range r {
 			v := f.Vector(i, j)
 			d := math.Hypot(v.X, v.Y)
 			if math.IsNaN(d) {
@@ -93,7 +93,7 @@ func (f *Field) Plot(c draw.Canvas, plt *plot.Plot) {
 	trX, trY := plt.Transforms(&c)
 
 	cols, rows := f.FieldXY.Dims()
-	for i := 0; i < cols; i++ {
+	for i := range cols {
 		var right, left float64
 		switch i {
 		case 0:
@@ -111,7 +111,7 @@ func (f *Field) Plot(c draw.Canvas, plt *plot.Plot) {
 			left = -(f.FieldXY.X(i) - f.FieldXY.X(i-1)) / 2
 		}
 
-		for j := 0; j < rows; j++ {
+		for j := range rows {
 			var up, down float64
 			switch j {
 			case 0:
@@ -200,8 +200,8 @@ func (f *Field) DataRange() (xmin, xmax, ymin, ymax float64) {
 func (f *Field) GlyphBoxes(plt *plot.Plot) []plot.GlyphBox {
 	c, r := f.FieldXY.Dims()
 	b := make([]plot.GlyphBox, 0, r*c)
-	for i := 0; i < c; i++ {
-		for j := 0; j < r; j++ {
+	for i := range c {
+		for j := range r {
 			b = append(b, plot.GlyphBox{
 				X: plt.X.Norm(f.FieldXY.X(i)),
 				Y: plt.Y.Norm(f.FieldXY.Y(j)),

plotter/heat.go

@@ -81,8 +81,8 @@ func NewHeatMap(g GridXYZ, p palette.Palette) *HeatMap {
 	default:
 		min, max = math.Inf(1), math.Inf(-1)
 		c, r := g.Dims()
-		for i := 0; i < c; i++ {
-			for j := 0; j < r; j++ {
+		for i := range c {
+			for j := range r {
 				v := g.Z(i, j)
 				if math.IsNaN(v) {
 					continue
@@ -120,8 +120,8 @@ func (h *HeatMap) plotRasterized(c draw.Canvas, plt *plot.Plot) {
 
 	pal := h.Palette.Colors()
 	ps := float64(len(pal)-1) / (h.Max - h.Min)
-	for i := 0; i < cols; i++ {
-		for j := 0; j < rows; j++ {
+	for i := range cols {
+		for j := range rows {
 			var col color.Color
 			switch v := h.GridXYZ.Z(i, j); {
 			case v < h.Min:
@@ -161,7 +161,7 @@ func (h *HeatMap) plotVectorized(c draw.Canvas, plt *plot.Plot) {
 
 	var pa vg.Path
 	cols, rows := h.GridXYZ.Dims()
-	for i := 0; i < cols; i++ {
+	for i := range cols {
 		var right, left float64
 		switch i {
 		case 0:
@@ -179,7 +179,7 @@ func (h *HeatMap) plotVectorized(c draw.Canvas, plt *plot.Plot) {
 			left = -(h.GridXYZ.X(i) - h.GridXYZ.X(i-1)) / 2
 		}
 
-		for j := 0; j < rows; j++ {
+		for j := range rows {
 			var up, down float64
 			switch j {
 			case 0:
@@ -258,8 +258,8 @@ func (h *HeatMap) DataRange() (xmin, xmax, ymin, ymax float64) {
 func (h *HeatMap) GlyphBoxes(plt *plot.Plot) []plot.GlyphBox {
 	c, r := h.GridXYZ.Dims()
 	b := make([]plot.GlyphBox, 0, r*c)
-	for i := 0; i < c; i++ {
-		for j := 0; j < r; j++ {
+	for i := range c {
+		for j := range r {
 			b = append(b, plot.GlyphBox{
 				X: plt.X.Norm(h.GridXYZ.X(i)),
 				Y: plt.Y.Norm(h.GridXYZ.Y(j)),

plotter/histogram.go

@@ -186,7 +186,7 @@ func binPoints(xys XYer, n int) (bins []HistogramBin, width float64) {
 	xmin, xmax := Range(XValues{xys})
 	if n <= 0 {
 		m := 0.0
-		for i := 0; i < xys.Len(); i++ {
+		for i := range xys.Len() {
 			_, y := xys.XY(i)
 			m += math.Max(y, 1.0)
 		}
@@ -207,7 +207,7 @@ func binPoints(xys XYer, n int) (bins []HistogramBin, width float64) {
 		bins[i].Max = xmin + float64(i+1)*w
 	}
 
-	for i := 0; i < xys.Len(); i++ {
+	for i := range xys.Len() {
 		x, y := xys.XY(i)
 		bin := int((x - xmin) / w)
 		if x == xmax {

plotter/histogram_example_test.go

@@ -31,7 +31,7 @@ func ExampleHistogram() {
 
 	n := 10000
 	vals := make(plotter.Values, n)
-	for i := 0; i < n; i++ {
+	for i := range n {
 		vals[i] = rnd.NormFloat64()
 	}
 

plotter/image.go

@@ -86,13 +86,13 @@ func (img *Image) transformFor(p *plot.Plot) image.Image {
 	}
 	b := img.img.Bounds()
 	o := image.NewNRGBA64(b)
-	for c := 0; c < img.cols; c++ {
+	for c := range img.cols {
 		// Find the equivalent image column after applying axis transforms.
 		cTrans := int(p.X.Norm(img.x(c)) * float64(img.cols))
 		// Find the equivalent column of the previous image column after applying
 		// axis transforms.
 		cPrevTrans := int(p.X.Norm(img.x(maxInt(c-1, 0))) * float64(img.cols))
-		for r := 0; r < img.rows; r++ {
+		for r := range img.rows {
 			// Find the equivalent image row after applying axis transforms.
 			rTrans := int(p.Y.Norm(img.y(r)) * float64(img.rows))
 			// Find the equivalent row of the previous image row after applying

plotter/plotter.go

@@ -55,7 +55,7 @@ type Valuer interface {
 func Range(vs Valuer) (min, max float64) {
 	min = math.Inf(1)
 	max = math.Inf(-1)
-	for i := 0; i < vs.Len(); i++ {
+	for i := range vs.Len() {
 		v := vs.Value(i)
 		min = math.Min(min, v)
 		max = math.Max(max, v)
@@ -93,7 +93,7 @@ func CopyValues(vs Valuer) (Values, error) {
 		return nil, ErrNoData
 	}
 	cpy := make(Values, vs.Len())
-	for i := 0; i < vs.Len(); i++ {
+	for i := range vs.Len() {
 		cpy[i] = vs.Value(i)
 		if err := CheckFloats(cpy[i]); err != nil {
 			return nil, err

plotter/polygon_example_test.go

@@ -121,9 +121,9 @@ func ExamplePolygon_hexagons() {
 	for i, xmin := range xstart {
 		ymin := ystart[i]
 		x := xmin
-		for ix := 0; ix < nx; ix++ {
+		for range nx {
 			y := ymin
-			for iy := 0; iy < ny; iy++ {
+			for range ny {
 				var poly *plotter.Polygon
 				poly, err = plotter.NewPolygon(hex(x, y, r))
 				if err != nil {

plotter/quartile_example_test.go

@@ -22,7 +22,7 @@ func ExampleQuartPlot() {
 	uniform := make(plotter.Values, n)
 	normal := make(plotter.Values, n)
 	expon := make(plotter.Values, n)
-	for i := 0; i < n; i++ {
+	for i := range n {
 		uniform[i] = rnd.Float64()
 		normal[i] = rnd.NormFloat64()
 		expon[i] = rnd.ExpFloat64()

plotter/rotation_example_test.go

@@ -24,7 +24,7 @@ func Example_rotation() {
 	// Sin creates a sine curve.
 	sin := func(n int, xmax float64) plotter.XYs {
 		xy := make(plotter.XYs, n)
-		for i := 0; i < n; i++ {
+		for i := range n {
 			xy[i].X = xmax / float64(n) * float64(i)
 			xy[i].Y = math.Sin(xy[i].X) * 100
 		}