Pie & Donut Chart

When to use

Pie charts work best when:

You have a small number of categories (≤ 6) and the relative proportions are what matters.
You want to highlight one dominant segment.

Donut charts are the same chart with a circular cutout — they reduce the visual weight of the centre and are a common alternative to the solid pie.

Use ax.Pie(labels, values, chart.PieStyle{...}).

Basic example

package main

import (
	"github.com/goplotlib/goplotlib/chart"
	"github.com/goplotlib/goplotlib/plot"
)

func main() {
	labels := []string{"Direct", "Organic Search", "Referral", "Social", "Email"}
	values := []float64{35, 28, 18, 12, 7}

	fig := plot.New(plot.WithWidth(700), plot.WithHeight(420))
	ax := fig.AddAxes()
	ax.Pie(labels, values, chart.PieStyle{})
	ax.SetTitle("Traffic Sources")
}

Pie chart

Donut variant

Set DonutRadius to the inner hole radius as a proportion of the outer radius (0 = solid pie, 0.55 = typical donut).

package main

import (
	"github.com/goplotlib/goplotlib/chart"
	"github.com/goplotlib/goplotlib/plot"
)

func main() {
	labels := []string{"Direct", "Organic Search", "Referral", "Social", "Email"}
	values := []float64{35, 28, 18, 12, 7}

	fig := plot.New(plot.WithWidth(700), plot.WithHeight(420))
	ax := fig.AddAxes()
	ax.Pie(labels, values, chart.PieStyle{DonutRadius: 0.55})
	ax.SetTitle("Traffic Sources (Donut)")
}

Donut chart

Exploding a segment

Set ExplodeIdx and ExplodeOffset to offset a segment outward along its midpoint angle, drawing attention to it.

ax.Pie(labels, values, chart.PieStyle{
	DonutRadius:   0.55,
	ExplodeIdx:    0,  // explode the first segment
	ExplodeOffset: 12, // by 12 px
})

Notes

Segment labels are drawn outside the circle for segments that are ≥ 5 % of the total; smaller segments are unlabelled.
Colors are assigned automatically from the active theme’s palette.
Pie charts occupy the full cell area — no axes, grid lines, or spines are drawn.

Style reference

chart.PieStyle fields:

Field	Type	Default	Description
`DonutRadius`	`float64`	`0`	Inner radius as fraction of outer; `0` = solid pie
`ExplodeIdx`	`int`	`0`	Index of segment to offset outward
`ExplodeOffset`	`float64`	`0`	Outward offset in pixels for the exploded segment

Heatmap Box Plot