plot/plotter/boxplot.go at master · gonum/plot · GitHub

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// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

package plotter

import (

"errors"

"image/color"

"math"

"sort"

"gonum.org/v1/plot"

"gonum.org/v1/plot/vg"

"gonum.org/v1/plot/vg/draw"

)

// fiveStatPlot contains the shared fields for quartile

// and box-whisker plots.

type fiveStatPlot struct {

// Values is a copy of the values of the values used to

// create this box plot.

Values

// Location is the location of the box along its axis.

Location float64

// Median is the median value of the data.

Median float64

// Quartile1 and Quartile3 are the first and

// third quartiles of the data respectively.

Quartile1, Quartile3 float64

// AdjLow and AdjHigh are the `adjacent' values

// on the low and high ends of the data. The

// adjacent values are the points to which the

// whiskers are drawn.

AdjLow, AdjHigh float64

// Min and Max are the extreme values of the data.

Min, Max float64

// Outside are the indices of Vs for the outside points.

Outside []int

}

// BoxPlot implements the Plotter interface, drawing

// a boxplot to represent the distribution of values.

type BoxPlot struct {

fiveStatPlot

// Offset is added to the x location of each box.

// When the Offset is zero, the boxes are drawn

// centered at their x location.

Offset vg.Length

// Width is the width used to draw the box.

Width vg.Length

// CapWidth is the width of the cap used to top

// off a whisker.

CapWidth vg.Length

// GlyphStyle is the style of the outside point glyphs.

GlyphStyle draw.GlyphStyle

// FillColor is the color used to fill the box.

// The default is no fill.

FillColor color.Color

// BoxStyle is the line style for the box.

BoxStyle draw.LineStyle

// MedianStyle is the line style for the median line.

MedianStyle draw.LineStyle

// WhiskerStyle is the line style used to draw the

// whiskers.

WhiskerStyle draw.LineStyle

// Horizontal dictates whether the BoxPlot should be in the vertical

// (default) or horizontal direction.

Horizontal bool

}

// NewBoxPlot returns a new BoxPlot that represents

// the distribution of the given values. The style of

// the box plot is that used for Tukey's schematic

// plots in “Exploratory Data Analysis.”

// An error is returned if the boxplot is created with

// no values.

// The fence values are 1.5x the interquartile before

// the first quartile and after the third quartile. Any

// value that is outside of the fences are drawn as

// Outside points. The adjacent values (to which the

// whiskers stretch) are the minimum and maximum

// values that are not outside the fences.

func NewBoxPlot(w vg.Length, loc float64, values Valuer) (*BoxPlot, error) {

if w < 0 {

return nil, errors.New("plotter: negative boxplot width")

}

b := new(BoxPlot)

var err error

if b.fiveStatPlot, err = newFiveStat(w, loc, values); err != nil {

return nil, err

}

b.Width = w

b.CapWidth = 3 * w / 4

b.GlyphStyle = DefaultGlyphStyle

b.BoxStyle = DefaultLineStyle

b.MedianStyle = DefaultLineStyle

b.WhiskerStyle = draw.LineStyle{

Width: vg.Points(0.5),

Dashes: []vg.Length{vg.Points(4), vg.Points(2)},

}

if len(b.Values) == 0 {

b.Width = 0

b.GlyphStyle.Radius = 0

b.BoxStyle.Width = 0

b.MedianStyle.Width = 0

b.WhiskerStyle.Width = 0

}

return b, nil

}

func newFiveStat(w vg.Length, loc float64, values Valuer) (fiveStatPlot, error) {

var b fiveStatPlot

b.Location = loc

var err error

if b.Values, err = CopyValues(values); err != nil {

return fiveStatPlot{}, err

}

sorted := make(Values, len(b.Values))

copy(sorted, b.Values)

sort.Float64s(sorted)

if len(sorted) == 1 {

b.Median = sorted[0]

b.Quartile1 = sorted[0]

b.Quartile3 = sorted[0]

} else {

b.Median = median(sorted)

b.Quartile1 = median(sorted[:len(sorted)/2])

b.Quartile3 = median(sorted[len(sorted)/2:])

}

b.Min = sorted[0]

b.Max = sorted[len(sorted)-1]

low := b.Quartile1 - 1.5*(b.Quartile3-b.Quartile1)

high := b.Quartile3 + 1.5*(b.Quartile3-b.Quartile1)

b.AdjLow = math.Inf(1)

b.AdjHigh = math.Inf(-1)

for i, v := range b.Values {

if v > high || v < low {

b.Outside = append(b.Outside, i)

continue

}

if v < b.AdjLow {

b.AdjLow = v

}

if v > b.AdjHigh {

b.AdjHigh = v

}

return b, nil

}

// median returns the median value from a

// sorted Values.

func median(vs Values) float64 {

if len(vs) == 1 {

return vs[0]

}

med := vs[len(vs)/2]

if len(vs)%2 == 0 {

med += vs[len(vs)/2-1]

med /= 2

}

return med

}

// Plot draws the BoxPlot on Canvas c and Plot plt.

func (b *BoxPlot) Plot(c draw.Canvas, plt *plot.Plot) {

if b.Horizontal {

b := &horizBoxPlot{b}

b.Plot(c, plt)

return

}

trX, trY := plt.Transforms(&c)

x := trX(b.Location)

if !c.ContainsX(x) {

return

}

x += b.Offset

med := trY(b.Median)

q1 := trY(b.Quartile1)

q3 := trY(b.Quartile3)

aLow := trY(b.AdjLow)

aHigh := trY(b.AdjHigh)

pts := []vg.Point{

{X: x - b.Width/2, Y: q1},

{X: x - b.Width/2, Y: q3},

{X: x + b.Width/2, Y: q3},

{X: x + b.Width/2, Y: q1},

{X: x - b.Width/2 - b.BoxStyle.Width/2, Y: q1},

}

box := c.ClipLinesY(pts)

if b.FillColor != nil {

c.FillPolygon(b.FillColor, c.ClipPolygonY(pts))

}

c.StrokeLines(b.BoxStyle, box...)

medLine := c.ClipLinesY([]vg.Point{

{X: x - b.Width/2, Y: med},

{X: x + b.Width/2, Y: med},

})

c.StrokeLines(b.MedianStyle, medLine...)

cap := b.CapWidth / 2

whisks := c.ClipLinesY(

[]vg.Point{{X: x, Y: q3}, {X: x, Y: aHigh}},

[]vg.Point{{X: x - cap, Y: aHigh}, {X: x + cap, Y: aHigh}},

[]vg.Point{{X: x, Y: q1}, {X: x, Y: aLow}},

[]vg.Point{{X: x - cap, Y: aLow}, {X: x + cap, Y: aLow}},

)

c.StrokeLines(b.WhiskerStyle, whisks...)

for _, out := range b.Outside {

y := trY(b.Value(out))

if c.ContainsY(y) {

c.DrawGlyphNoClip(b.GlyphStyle, vg.Point{X: x, Y: y})

}

// DataRange returns the minimum and maximum x

// and y values, implementing the plot.DataRanger

// interface.

func (b *BoxPlot) DataRange() (float64, float64, float64, float64) {

if b.Horizontal {

b := &horizBoxPlot{b}

return b.DataRange()

}

return b.Location, b.Location, b.Min, b.Max

}

// GlyphBoxes returns a slice of GlyphBoxes for the

// points and for the median line of the boxplot,

// implementing the plot.GlyphBoxer interface

func (b *BoxPlot) GlyphBoxes(plt *plot.Plot) []plot.GlyphBox {

if b.Horizontal {

b := &horizBoxPlot{b}

return b.GlyphBoxes(plt)

}

bs := make([]plot.GlyphBox, len(b.Outside)+1)

for i, out := range b.Outside {

bs[i].X = plt.X.Norm(b.Location)

bs[i].Y = plt.Y.Norm(b.Value(out))

bs[i].Rectangle = b.GlyphStyle.Rectangle()

}

bs[len(bs)-1].X = plt.X.Norm(b.Location)

bs[len(bs)-1].Y = plt.Y.Norm(b.Median)

bs[len(bs)-1].Rectangle = vg.Rectangle{

Min: vg.Point{X: b.Offset - (b.Width/2 + b.BoxStyle.Width/2)},

Max: vg.Point{X: b.Offset + (b.Width/2 + b.BoxStyle.Width/2)},

}

return bs

}

// OutsideLabels returns a *Labels that will plot

// a label for each of the outside points. The

// labels are assumed to correspond to the

// points used to create the box plot.

func (b *BoxPlot) OutsideLabels(labels Labeller) (*Labels, error) {

if b.Horizontal {

b := &horizBoxPlot{b}

return b.OutsideLabels(labels)

}

strs := make([]string, len(b.Outside))

for i, out := range b.Outside {

strs[i] = labels.Label(out)

}

o := boxPlotOutsideLabels{b, strs}

ls, err := NewLabels(o)

if err != nil {

return nil, err

}

off := 0.5 * b.GlyphStyle.Radius

ls.Offset = ls.Offset.Add(vg.Point{X: off, Y: off})

return ls, nil

}

type boxPlotOutsideLabels struct {

box *BoxPlot

labels []string

}

func (o boxPlotOutsideLabels) Len() int {

return len(o.box.Outside)

}

func (o boxPlotOutsideLabels) XY(i int) (float64, float64) {

return o.box.Location, o.box.Value(o.box.Outside[i])

}

func (o boxPlotOutsideLabels) Label(i int) string {

return o.labels[i]

}

// horizBoxPlot is like a regular BoxPlot, however,

// it draws horizontally instead of Vertically.

// TODO: Merge code for horizontal and vertical box plots as has been done for

// bar charts.

type horizBoxPlot struct{ *BoxPlot }

func (b horizBoxPlot) Plot(c draw.Canvas, plt *plot.Plot) {

trX, trY := plt.Transforms(&c)

y := trY(b.Location)

if !c.ContainsY(y) {

return

}

y += b.Offset

med := trX(b.Median)

q1 := trX(b.Quartile1)

q3 := trX(b.Quartile3)

aLow := trX(b.AdjLow)

aHigh := trX(b.AdjHigh)

pts := []vg.Point{

{X: q1, Y: y - b.Width/2},

{X: q3, Y: y - b.Width/2},

{X: q3, Y: y + b.Width/2},

{X: q1, Y: y + b.Width/2},

{X: q1, Y: y - b.Width/2 - b.BoxStyle.Width/2},

}

box := c.ClipLinesX(pts)

if b.FillColor != nil {

c.FillPolygon(b.FillColor, c.ClipPolygonX(pts))

}

c.StrokeLines(b.BoxStyle, box...)

medLine := c.ClipLinesX([]vg.Point{

{X: med, Y: y - b.Width/2},

{X: med, Y: y + b.Width/2},

})

c.StrokeLines(b.MedianStyle, medLine...)

cap := b.CapWidth / 2

whisks := c.ClipLinesX(

[]vg.Point{{X: q3, Y: y}, {X: aHigh, Y: y}},

[]vg.Point{{X: aHigh, Y: y - cap}, {X: aHigh, Y: y + cap}},

[]vg.Point{{X: q1, Y: y}, {X: aLow, Y: y}},

[]vg.Point{{X: aLow, Y: y - cap}, {X: aLow, Y: y + cap}},

)

c.StrokeLines(b.WhiskerStyle, whisks...)

for _, out := range b.Outside {

x := trX(b.Value(out))

if c.ContainsX(x) {

c.DrawGlyphNoClip(b.GlyphStyle, vg.Point{X: x, Y: y})

}

// DataRange returns the minimum and maximum x

// and y values, implementing the plot.DataRanger

// interface.

func (b horizBoxPlot) DataRange() (float64, float64, float64, float64) {

return b.Min, b.Max, b.Location, b.Location

}

// GlyphBoxes returns a slice of GlyphBoxes for the

// points and for the median line of the boxplot,

// implementing the plot.GlyphBoxer interface

func (b horizBoxPlot) GlyphBoxes(plt *plot.Plot) []plot.GlyphBox {

bs := make([]plot.GlyphBox, len(b.Outside)+1)

for i, out := range b.Outside {

bs[i].X = plt.X.Norm(b.Value(out))

bs[i].Y = plt.Y.Norm(b.Location)

bs[i].Rectangle = b.GlyphStyle.Rectangle()

}

bs[len(bs)-1].X = plt.X.Norm(b.Median)

bs[len(bs)-1].Y = plt.Y.Norm(b.Location)

bs[len(bs)-1].Rectangle = vg.Rectangle{

Min: vg.Point{Y: b.Offset - (b.Width/2 + b.BoxStyle.Width/2)},

Max: vg.Point{Y: b.Offset + (b.Width/2 + b.BoxStyle.Width/2)},

}

return bs

}

// OutsideLabels returns a *Labels that will plot

// a label for each of the outside points. The

// labels are assumed to correspond to the

// points used to create the box plot.

func (b *horizBoxPlot) OutsideLabels(labels Labeller) (*Labels, error) {

strs := make([]string, len(b.Outside))

for i, out := range b.Outside {

strs[i] = labels.Label(out)

}

o := horizBoxPlotOutsideLabels{

boxPlotOutsideLabels{b.BoxPlot, strs},

}

ls, err := NewLabels(o)

if err != nil {

return nil, err

}

off := 0.5 * b.GlyphStyle.Radius

ls.Offset = ls.Offset.Add(vg.Point{X: off, Y: off})

return ls, nil

}

type horizBoxPlotOutsideLabels struct {

boxPlotOutsideLabels

}

func (o horizBoxPlotOutsideLabels) XY(i int) (float64, float64) {

return o.box.Value(o.box.Outside[i]), o.box.Location

}

// ValueLabels implements both the Valuer

// and Labeller interfaces.

type ValueLabels []struct {

Value float64

Label string

}

// Len returns the number of items.

func (vs ValueLabels) Len() int {

return len(vs)

}

// Value returns the value of item i.

func (vs ValueLabels) Value(i int) float64 {

return vs[i].Value

}

// Label returns the label of item i.

func (vs ValueLabels) Label(i int) string {

return vs[i].Label

}

plot/plotter/boxplot.go at master · gonum/plot · GitHub

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