Bar Chart

When to use

Bar charts are the right choice when:

Your x-axis consists of named categories rather than numeric values.
You want to compare magnitudes across a small number of groups (typically 3–20).
The order of categories is meaningful (e.g., months, product lines).

Use ax.Bar(categories, values, chart.BarStyle{...}) to add a bar series.

Basic example

package main

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

func main() {
	categories := []string{"January", "February", "March", "April", "May", "June"}
	values := []float64{142.4, 168.9, 195.3, 181.7, 223.6, 247.1}

	fig := plot.New(
		plot.WithWidth(860),
		plot.WithHeight(420),
		plot.WithTheme(theme.FiveThirtyEight),
	)
	ax := fig.AddAxes()
	ax.Bar(categories, values, chart.BarStyle{Label: "Revenue ($ thousands)"})
	ax.SetTitle("Monthly Revenue — H1").SetYLabel("USD (thousands)")
}

Bar chart

Grouped bars

Multiple calls to ax.Bar with the same categories produce a grouped bar chart automatically:

package main

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

func main() {
	cats := []string{"Q1", "Q2", "Q3", "Q4"}

	fig := plot.New(plot.WithWidth(860), plot.WithHeight(420))
	ax := fig.AddAxes()
	ax.Bar(cats, []float64{120, 145, 162, 189}, chart.BarStyle{Label: "2023"})
	ax.Bar(cats, []float64{135, 158, 174, 210}, chart.BarStyle{Label: "2024"})
	ax.SetTitle("Grouped Bar — Revenue by Quarter").SetYLabel("Revenue ($k)")
}

Grouped bar chart

Negative values

Bars with negative values extend below the baseline automatically:

package main

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

func main() {
	cats := []string{"Jan", "Feb", "Mar", "Apr", "May", "Jun"}
	vals := []float64{12, -8, 22, -5, 18, 30}

	fig := plot.New(plot.WithWidth(860), plot.WithHeight(420))
	ax := fig.AddAxes()
	ax.Bar(cats, vals, chart.BarStyle{Label: "profit/loss"})
	ax.SetTitle("Monthly Profit / Loss").SetYLabel("$k")
	ax.HLine(0)
}

Bar chart with negatives

Square bars

By default bars have rounded top corners. Set SquareBars: true to disable this:

ax.Bar(cats, vals, chart.BarStyle{Label: "revenue", SquareBars: true})

Style reference

chart.BarStyle fields:

Field	Type	Default	Description
`Label`	`string`	`""`	Series label shown in the legend
`Color`	`color.Color`	palette	Override the automatic palette color
`Opacity`	`float64`	`1.0`	Overall bar opacity, 0.0–1.0
`SquareBars`	`bool`	`false`	Set `true` to disable the default rounded corners

Notes

The y-axis always includes zero so the baseline is unambiguous.
Bar width is computed automatically from the number of categories.
For horizontal bars, see Horizontal Bar Chart.
For stacked bars, see Stacked Bar Chart.

Line Chart Scatter Plot