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Add ability to draw bar chart X-axis at BaseValue

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This commit is contained in:
Alan Bernstein 2020-08-20 23:29:13 -05:00
parent 962b9abdec
commit 8310896cd0
2 changed files with 20 additions and 13 deletions
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27
bar_chart.go
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@ -30,8 +30,9 @@ type BarChart struct {
BarSpacing int BarSpacing int
UseBaseValue bool UseBaseValue bool
BaseValue float64 BaseValue float64
UseBaseValueXAxis bool
Font *truetype.Font Font *truetype.Font
defaultFont *truetype.Font defaultFont *truetype.Font
@ -130,7 +131,7 @@ func (bc BarChart) Render(rp RendererProvider, w io.Writer) error {
} }
bc.drawCanvas(r, canvasBox) bc.drawCanvas(r, canvasBox)
bc.drawBars(r, canvasBox, yr) bc.drawBars(r, canvasBox, yr)
bc.drawXAxis(r, canvasBox) bc.drawXAxis(r, canvasBox, yr)
bc.drawYAxis(r, canvasBox, yr, yt) bc.drawYAxis(r, canvasBox, yr, yt)
bc.drawTitle(r) bc.drawTitle(r)
@ -223,25 +224,29 @@ func (bc BarChart) drawBars(r Renderer, canvasBox Box, yr Range) {
} }
} }
func (bc BarChart) drawXAxis(r Renderer, canvasBox Box) { func (bc BarChart) drawXAxis(r Renderer, canvasBox Box, yr Range) {
if !bc.XAxis.Hidden { if !bc.XAxis.Hidden {
axisStyle := bc.XAxis.InheritFrom(bc.styleDefaultsAxes()) axisStyle := bc.XAxis.InheritFrom(bc.styleDefaultsAxes())
axisStyle.WriteToRenderer(r) axisStyle.WriteToRenderer(r)
width, spacing, _ := bc.calculateScaledTotalWidth(canvasBox) width, spacing, _ := bc.calculateScaledTotalWidth(canvasBox)
r.MoveTo(canvasBox.Left, canvasBox.Bottom) axisYValue := canvasBox.Bottom
r.LineTo(canvasBox.Right, canvasBox.Bottom) if bc.UseBaseValueXAxis {
axisYValue -= yr.Translate(bc.BaseValue)
}
r.MoveTo(canvasBox.Left, axisYValue)
r.LineTo(canvasBox.Right, axisYValue)
r.Stroke() r.Stroke()
r.MoveTo(canvasBox.Left, canvasBox.Bottom) r.MoveTo(canvasBox.Left, axisYValue)
r.LineTo(canvasBox.Left, canvasBox.Bottom+DefaultVerticalTickHeight) r.LineTo(canvasBox.Left, axisYValue+DefaultVerticalTickHeight)
r.Stroke() r.Stroke()
cursor := canvasBox.Left cursor := canvasBox.Left
for index, bar := range bc.Bars { for index, bar := range bc.Bars {
barLabelBox := Box{ barLabelBox := Box{
Top: canvasBox.Bottom + DefaultXAxisMargin, Top: axisYValue + DefaultXAxisMargin,
Left: cursor, Left: cursor,
Right: cursor + width + spacing, Right: cursor + width + spacing,
Bottom: bc.GetHeight(), Bottom: bc.GetHeight(),
@ -253,8 +258,8 @@ func (bc BarChart) drawXAxis(r Renderer, canvasBox Box) {
axisStyle.WriteToRenderer(r) axisStyle.WriteToRenderer(r)
if index < len(bc.Bars)-1 { if index < len(bc.Bars)-1 {
r.MoveTo(barLabelBox.Right, canvasBox.Bottom) r.MoveTo(barLabelBox.Right, axisYValue)
r.LineTo(barLabelBox.Right, canvasBox.Bottom+DefaultVerticalTickHeight) r.LineTo(barLabelBox.Right, axisYValue+DefaultVerticalTickHeight)
r.Stroke() r.Stroke()
} }
cursor += width + spacing cursor += width + spacing

6
examples/bar_chart_base_value/main.go
View file

@ -31,6 +31,7 @@ func main() {
}, },
Height: 512, Height: 512,
BarWidth: 60, BarWidth: 60,
XAxis: chart.Style{StrokeColor: drawing.ColorBlack, StrokeWidth: 1.0},
YAxis: chart.YAxis{ YAxis: chart.YAxis{
Ticks: []chart.Tick{ Ticks: []chart.Tick{
{Value: -4.0, Label: "-4"}, {Value: -4.0, Label: "-4"},
@ -44,8 +45,9 @@ func main() {
{Value: 12.0, Label: "12"}, {Value: 12.0, Label: "12"},
}, },
}, },
UseBaseValue: true, UseBaseValue: true,
BaseValue: 0.0, BaseValueXAxis: true,
BaseValue: 0.0,
Bars: []chart.Value{ Bars: []chart.Value{
{Value: 10.0, Style: profitStyle, Label: "Profit"}, {Value: 10.0, Style: profitStyle, Label: "Profit"},
{Value: 12.0, Style: profitStyle, Label: "More Profit"}, {Value: 12.0, Style: profitStyle, Label: "More Profit"},