Documentation
¶
Overview ¶
Package ggplot is a production-grade, pure-Go Grammar of Graphics plotting library.
Inspired by R's ggplot2, it provides a declarative, composable API for building statistical visualizations from data, aesthetics, geometries, scales, coordinate systems, facets, and themes.
Quick Start ¶
p := ggplot.New(ds,
aes.X("x"),
aes.Y("y"),
aes.Color("group"),
).
Layer(geom.Point(geom.WithSize(4), geom.WithAlpha(0.7))).
Layer(geom.Smooth()).
Labs(ggplot.Title("My Plot"), ggplot.XLab("X Axis")).
Theme("minimal").
Save("output.png", 1200, 800)
Architecture ¶
The library follows a strict pipeline:
PlotSpec -> Validate -> Stat Transform -> Scale Training -> Layout -> Render
All data flows through the dataset.Dataset abstraction. Multiple engine backends are supported: memory (Go slices), Apache Arrow (columnar arrays), and BigQuery (SQL pushdown). Arrow IPC and Parquet ingest provide zero-copy reads; constructing from Go slices requires one copy.
Index ¶
- Constants
- Variables
- func RegisterDrawer(t geom.Type, d Drawer)
- type AesMap
- type Built
- func (b *Built) Draw(ctx context.Context, cv canvas.Canvas, width, height int) error
- func (b *Built) DrawCanvas(ctx context.Context, width, height int) (*canvas.GGCanvas, error)
- func (b *Built) Explain() string
- func (b *Built) Labels() Labels
- func (b *Built) LayerData(panel, layer int) dataset.Dataset
- func (b *Built) NumLayers(panel int) int
- func (b *Built) NumPanels() int
- func (b *Built) PanelLayout() Layout
- func (b *Built) PipelineFor(panel, layer int) []string
- func (b *Built) Save(ctx context.Context, filename string, width, height int, opts ...RenderOpt) error
- func (b *Built) Theme() theme.Theme
- func (b *Built) WriteTo(ctx context.Context, w io.Writer, format string, width, height int, ...) (int64, error)
- type BuiltLayer
- type BuiltPanel
- type ColorBarSpec
- type DrawContext
- type Drawer
- type DrawerFunc
- type LabOpt
- type Labels
- type LayerSpec
- type Layout
- type LegendEntry
- type LegendPos
- type PanelLayout
- type Plot
- func (p *Plot) Aes(mappings ...aes.Mapping) *Plot
- func (p *Plot) Build(ctx context.Context) (*Built, error)
- func (p *Plot) Coord(c coord.Coord) *Plot
- func (p *Plot) CoordFlip() *Plot
- func (p *Plot) FacetGrid(rowCol, colCol string) *Plot
- func (p *Plot) FacetWrap(col string, opts ...facet.WrapOpt) *Plot
- func (p *Plot) Labs(opts ...LabOpt) *Plot
- func (p *Plot) Layer(l geom.Layer, localAes ...aes.Mapping) *Plot
- func (p *Plot) LegendPosition(pos LegendPos) *Plot
- func (p *Plot) Save(ctx context.Context, filename string, width, height int, opts ...RenderOpt) error
- func (p *Plot) ScaleColor(c colormap.Cmap) *Plot
- func (p *Plot) ScaleColorContinuous(c colormap.Cmap, n colormap.Norm) *Plot
- func (p *Plot) ScaleColorManual(m map[string]colormap.Color) *Plot
- func (p *Plot) ScaleFill(c colormap.Cmap) *Plot
- func (p *Plot) ScaleX(scaleType scale.Type, opts ...scale.Opt) *Plot
- func (p *Plot) ScaleY(scaleType scale.Type, opts ...scale.Opt) *Plot
- func (p *Plot) Theme(name theme.Name) *Plot
- func (p *Plot) WriteTo(ctx context.Context, w io.Writer, format string, width, height int, ...) (int64, error)
- func (p *Plot) XLim(lo, hi float64) *Plot
- func (p *Plot) YLim(lo, hi float64) *Plot
- type PlotSpec
- type RenderOpt
- type ScaleOverride
Constants ¶
const ( ColPANEL = "PANEL" // int64 -- facet panel index (0-based) ColGroup = "group" // int64 -- group index within a panel (0-based) )
System column names reserved by the build pipeline. These columns are injected into every layer's dataset during Build.
Variables ¶
var ( // ErrUnsupportedFormat is returned for unsupported output formats. ErrUnsupportedFormat = errors.New("ggplot: unsupported output format") // ErrRenderFailed is returned when rendering fails. ErrRenderFailed = errors.New("ggplot: render failed") // ErrNoLayers is returned when there are no layers to render. ErrNoLayers = errors.New("ggplot: no layers to render") // ErrMissingAesthetic is returned when a required aesthetic is missing. ErrMissingAesthetic = errors.New("ggplot: missing required aesthetic") // ErrInvalidConfig is returned for invalid plot configuration. ErrInvalidConfig = errors.New("ggplot: invalid configuration") )
Sentinel errors for the ggplot package.
Functions ¶
Types ¶
type AesMap ¶ added in v0.0.4
AesMap maps aesthetic channel names to column names.
func ToAesMap ¶ added in v0.0.4
ToAesMap converts a slice of aes.Mapping into an AesMap.
type Built ¶ added in v0.0.4
type Built struct {
// contains filtered or unexported fields
}
Built is the result of Plot.Build. It holds fully resolved layer data, trained scales, layout geometry, and theme — everything needed to draw without re-running the grammar pipeline.
This is the Go equivalent of ggplot2's ggplot_build(plot) → built.
func (*Built) Draw ¶ added in v0.0.4
Draw renders the built plot onto the given canvas at the specified dimensions.
This is the Go equivalent of ggplot2's grid.draw(ggplot_gtable(built)).
func (*Built) DrawCanvas ¶ added in v0.0.4
DrawCanvas creates a new canvas.GGCanvas and draws the built plot onto it. The caller owns the returned canvas and must call canvas.GGCanvas.Close when finished to release GPU resources.
func (*Built) Explain ¶ added in v0.0.5
Explain returns a human-readable summary of the built plot's structure, including panels, layers, transform pipelines, and output hints.
func (*Built) LayerData ¶ added in v0.0.4
LayerData returns the resolved dataset for the given layer in the given panel. This is the data each geom actually sees after stat/position transforms — the primary introspection API for debugging and platform-independent testing.
func (*Built) NumLayers ¶ added in v0.0.4
NumLayers returns the number of resolved layers in the given panel.
func (*Built) PanelLayout ¶ added in v0.0.4
PanelLayout returns the layout geometry.
func (*Built) PipelineFor ¶ added in v0.0.5
PipelineFor returns the ordered transform names for the given panel and layer. Panel and layer indices are zero-based.
func (*Built) Save ¶ added in v0.0.4
func (b *Built) Save(ctx context.Context, filename string, width, height int, opts ...RenderOpt) error
Save renders the built plot to a file. Format is inferred from extension. If height ≤ 0, it is inferred from width and the y-scale type:
- continuous y: width / φ (golden ratio ≈ 1.618)
- discrete y: 18px per category, clamped to [240, width]
Supported extensions:
.png — raster PNG (default) .svg — SVG 1.1 vector .pdf — PDF 1.4 vector
Options: WithScale for HiDPI output.
func (*Built) WriteTo ¶ added in v0.0.4
func (b *Built) WriteTo(ctx context.Context, w io.Writer, format string, width, height int, opts ...RenderOpt) (int64, error)
WriteTo writes the built plot to w in the given format. Supported formats: "png" (default), "svg", "pdf". If height ≤ 0, it is inferred from width (see Built.Save for rules). Options: WithScale for HiDPI output. Returns the number of bytes written.
type BuiltLayer ¶ added in v0.0.4
type BuiltLayer struct {
Geom geom.Layer
Data dataset.Dataset
Mapping AesMap
ContColorCol string
ContColScale *colormap.Scale
}
BuiltLayer holds one resolved layer's data after stat transform and grouping. The Data dataset always contains the system column PANEL (int64). When the layer was produced by group splitting, the system column group (int64) is also present.
type BuiltPanel ¶ added in v0.0.4
type BuiltPanel struct {
Label string
Layers []BuiltLayer
XScale scale.Scale
YScale scale.Scale
LegendEntries []LegendEntry
LegendTitle string
ColorBarSpec *ColorBarSpec
XIsDiscrete bool
}
BuiltPanel holds one facet panel with its resolved layers and trained scales.
type ColorBarSpec ¶ added in v0.0.4
ColorBarSpec describes a continuous color bar legend.
Cmap and Norm replace the previous opaque ColorFunc field: the bar walks Cmap.At directly across the [0,1] range, and Norm provides the data-space labels at the endpoints (and any future intermediate ticks).
type DrawContext ¶
type DrawContext struct {
Canvas canvas.Canvas
Coord coord.Coord
Data dataset.Dataset
Mapping AesMap
Params geom.Params
Theme theme.Theme // active theme for default styling
ContColorCol string // continuous color column (empty if none)
ContScale *colormap.Scale // continuous color scale (nil if none)
W, H float64 // panel size in pixels
XMin, XMax float64 // data domain bounds
YMin, YMax float64 // data domain bounds
}
DrawContext holds the rendering parameters passed to a Drawer. It encapsulates the canvas, coordinate system, data, aesthetic mappings, and panel bounds so that Drawer implementations are self-contained.
type Drawer ¶
type Drawer interface {
Draw(ctx DrawContext)
}
Drawer renders a geometry type onto the canvas. Implementations are registered via RegisterDrawer and looked up by geom.Type during rendering.
type DrawerFunc ¶
type DrawerFunc func(DrawContext)
DrawerFunc is an adapter to allow use of ordinary functions as [Drawer]s.
type Layout ¶ added in v0.0.4
type Layout struct {
Rows int
Cols int
Panels []PanelLayout
}
Layout holds the panel grid dimensions derived from faceting.
type LegendEntry ¶ added in v0.0.4
LegendEntry describes one item in the legend.
type PanelLayout ¶ added in v0.0.4
PanelLayout holds per-panel geometry and trained scale state.
type Plot ¶
type Plot struct {
// contains filtered or unexported fields
}
Plot is the immutable, declarative plot builder. Every method returns a new Plot with the modification applied, enabling a fluent chaining style.
Plot is safe to share and reuse - modifying a derived plot does not affect the original.
func (*Plot) Build ¶ added in v0.0.4
Build resolves the plot specification through the grammar pipeline and returns a *Built containing fully resolved layer data, trained scales, layout geometry, and theme. The result can be inspected via Built.LayerData or rendered via Built.Draw.
This is the Go equivalent of ggplot2's ggplot_build(plot).
func (*Plot) CoordFlip ¶
CoordFlip swaps the x and y axes. This is sugar for setting geom.Horizontal orientation on all layers and swapping the axis labels.
func (*Plot) Layer ¶
Layer adds a geometry layer to the plot with optional per-layer aesthetic overrides.
func (*Plot) LegendPosition ¶
LegendPosition sets the legend placement.
func (*Plot) Save ¶
func (p *Plot) Save(ctx context.Context, filename string, width, height int, opts ...RenderOpt) error
Save renders the plot to a file at the given dimensions. If height ≤ 0, it is inferred from width (see Built.Save for rules). The output format is inferred from the file extension:
.png — raster PNG (default) .svg — SVG 1.1 vector .pdf — PDF 1.4 vector
Options: WithScale for HiDPI output.
func (*Plot) ScaleColor ¶
ScaleColor configures the color aesthetic to use the given colormap. The cmap is composed with a default LinearNorm for continuous data, or used as a Listed palette for discrete data. Pass nil to clear an existing override and fall back to defaults.
func (*Plot) ScaleColorContinuous ¶
ScaleColorContinuous installs an explicit continuous color scale composed of the given Cmap and Norm. Use this to control LogNorm / TwoSlopeNorm / PowerNorm / data-range limits beyond the simple Plot.ScaleColor form.
func (*Plot) ScaleColorManual ¶
ScaleColorManual maps category labels to specific colors. Categories not in m fall back to the default Tab10 palette in the order they are encountered during dataset training.
func (*Plot) ScaleFill ¶
ScaleFill is the fill-aesthetic counterpart of Plot.ScaleColor.
func (*Plot) ScaleX ¶
ScaleX sets the x-axis scale type with optional configuration. Options: scale.WithBreaks, scale.WithLabels, scale.WithFormatter, scale.WithExpand, scale.WithMinorBreaks, scale.WithClipBounds.
func (*Plot) ScaleY ¶
ScaleY sets the y-axis scale type with optional configuration. Options: scale.WithBreaks, scale.WithLabels, scale.WithFormatter, scale.WithExpand, scale.WithMinorBreaks, scale.WithClipBounds.
func (*Plot) WriteTo ¶
func (p *Plot) WriteTo(ctx context.Context, w io.Writer, format string, width, height int, opts ...RenderOpt) (int64, error)
WriteTo renders the plot and writes the output to w in the given format. Supported formats: "png" (default), "svg", "pdf". If height ≤ 0, it is inferred from width (see Built.Save for rules). Options: WithScale for HiDPI output. Returns the number of bytes written.
Shorthand for Plot.Build followed by Built.WriteTo.
type PlotSpec ¶ added in v0.0.4
type PlotSpec struct {
// Dataset is the primary data source.
Dataset dataset.Dataset
// GlobalMapping maps aesthetic channels to column names at the plot level.
// Per-layer mappings override these.
GlobalMapping AesMap
// Layers describes each visual layer (geom + stat + position + local aes).
Layers []LayerSpec
// ScaleOverrides holds user-specified scale configurations, keyed by
// aesthetic channel ("x", "y", "color", etc.).
ScaleOverrides map[string]ScaleOverride
// ColorScales holds user-specified color/fill scales, keyed by
// aesthetic channel ("color" or "fill"). nil entries fall back to
// the auto-detected default ([colormap.Viridis] for continuous data,
// [colormap.Tab10] for discrete data).
ColorScales map[string]*colormap.Scale
// Coord defines the coordinate system (default: Cartesian).
Coord coord.Coord
// Facet defines the faceting strategy (default: None).
Facet facet.Facet
// Theme holds the theme name or configuration.
ThemeName theme.Name
// Labels holds plot title, subtitle, axis labels, caption.
Labels Labels
// XLim and YLim hold optional user-specified axis limits.
// nil means auto-detect from data.
XLim [2]*float64
YLim [2]*float64
// LegendPosition controls where the legend is drawn.
LegendPosition string
}
PlotSpec is the fully declarative specification of a plot, produced by the user-facing builder API and consumed by the compilation pipeline.
type RenderOpt ¶
type RenderOpt func(*renderConfig)
RenderOpt configures rendering output (scale, DPI, etc.).
type ScaleOverride ¶ added in v0.0.4
type ScaleOverride struct {
Type scale.Type // e.g., scale.Log10, scale.Sqrt, scale.Reverse
Params map[string]string // type-specific parameters
Opts []scale.Opt // functional options (WithBreaks, WithLabels, etc.)
}
ScaleOverride captures a user-requested scale for a specific aesthetic channel.
Directories
¶
| Path | Synopsis |
|---|---|
|
Package aes provides aesthetic mapping constructors for the Grammar of Graphics.
|
Package aes provides aesthetic mapping constructors for the Grammar of Graphics. |
|
Package canvas defines the rendering backend abstraction.
|
Package canvas defines the rendering backend abstraction. |
|
Package colormap provides a matplotlib-style colormap and color-scale API for the ggplot grammar of graphics pipeline.
|
Package colormap provides a matplotlib-style colormap and color-scale API for the ggplot grammar of graphics pipeline. |
|
Package coord defines coordinate systems that control how data positions are mapped to the 2D plotting surface.
|
Package coord defines coordinate systems that control how data positions are mapped to the 2D plotting surface. |
|
Package dataset provides columnar data abstractions for the Grammar of Graphics pipeline.
|
Package dataset provides columnar data abstractions for the Grammar of Graphics pipeline. |
|
arrow
Package arrow provides an Apache Arrow-backed compute engine for the dataset package.
|
Package arrow provides an Apache Arrow-backed compute engine for the dataset package. |
|
bigquery
Package bigquery implements a BigQuery SQL pushdown engine for the dataset library.
|
Package bigquery implements a BigQuery SQL pushdown engine for the dataset library. |
|
compute
Package compute provides portable SIMD primitives for the dataset engines.
|
Package compute provides portable SIMD primitives for the dataset engines. |
|
csv
Package csv provides CSV reading and writing for the dataset package.
|
Package csv provides CSV reading and writing for the dataset package. |
|
math
Package math provides SIMD-accelerated mathematical transforms for the dataset engines.
|
Package math provides SIMD-accelerated mathematical transforms for the dataset engines. |
|
memory
Package memory provides a lightweight Go-slice-backed compute engine for the dataset package.
|
Package memory provides a lightweight Go-slice-backed compute engine for the dataset package. |
|
parquet
Package parquet provides Parquet reading and writing for the dataset package.
|
Package parquet provides Parquet reading and writing for the dataset package. |
|
sort
Package sort provides SIMD-accelerated sorting for the dataset engines.
|
Package sort provides SIMD-accelerated sorting for the dataset engines. |
|
examples
|
|
|
annotations
command
Example: Reference lines and text annotations.
|
Example: Reference lines and text annotations. |
|
butterfly
command
Example: Butterfly curve with continuous color gradient.
|
Example: Butterfly curve with continuous color gradient. |
|
categorical
command
Example: Boxplot and Categorical (Discrete) X Axis
|
Example: Boxplot and Categorical (Discrete) X Axis |
|
clifford
command
Example: (Clifford[https://paulbourke.net/fractals/clifford/] attractor with continuous color gradient.
|
Example: (Clifford[https://paulbourke.net/fractals/clifford/] attractor with continuous color gradient. |
|
color_mapping
command
Example: Multi-Group Scatter with Colour Mapping and Legend
|
Example: Multi-Group Scatter with Colour Mapping and Legend |
|
coord_flip
command
Example: Orientation — every geometry flipped to horizontal.
|
Example: Orientation — every geometry flipped to horizontal. |
|
geometries/area
command
Example area demonstrates the geom.area geometry.
|
Example area demonstrates the geom.area geometry. |
|
geometries/bar
command
Example bar demonstrates the geom.bar geometry.
|
Example bar demonstrates the geom.bar geometry. |
|
geometries/errorbar
command
Example errorbar demonstrates the geom.ErrorBar geometry for showing measurement uncertainty with vertical bars and caps.
|
Example errorbar demonstrates the geom.ErrorBar geometry for showing measurement uncertainty with vertical bars and caps. |
|
geometries/histogram
command
Example histogram demonstrates the geom.histogram geometry.
|
Example histogram demonstrates the geom.histogram geometry. |
|
geometries/line
command
Example line demonstrates the geom.line geometry.
|
Example line demonstrates the geom.line geometry. |
|
geometries/point
command
Example point demonstrates the geom.point geometry.
|
Example point demonstrates the geom.point geometry. |
|
geometries/polygon
command
Example polygon demonstrates the geom.Polygon geometry for drawing closed filled shapes from grouped x/y coordinates.
|
Example polygon demonstrates the geom.Polygon geometry for drawing closed filled shapes from grouped x/y coordinates. |
|
geometries/segment
command
Example segment demonstrates the geom.Segment geometry for drawing line segments from (x, y) to (xend, yend).
|
Example segment demonstrates the geom.Segment geometry for drawing line segments from (x, y) to (xend, yend). |
|
geometries/smooth
command
Example smooth demonstrates the geom.smooth geometry.
|
Example smooth demonstrates the geom.smooth geometry. |
|
geometries/tile
command
Example tile demonstrates the geom.Tile heatmap geometry.
|
Example tile demonstrates the geom.Tile heatmap geometry. |
|
multiline
command
Example: Multi-Line Plot
|
Example: Multi-Line Plot |
|
phase2_features
command
Phase 2: Coordinates, Faceting, Themes, Guides, Aesthetics, LegendPosition
|
Phase 2: Coordinates, Faceting, Themes, Guides, Aesthetics, LegendPosition |
|
phase2_geometries
command
Phase 2: Geometries — Point, Line, Step, Bar, Histogram, Area, Density, Rug, HLine, VLine, Text, BoxPlot, Smooth
|
Phase 2: Geometries — Point, Line, Step, Bar, Histogram, Area, Density, Rug, HLine, VLine, Text, BoxPlot, Smooth |
|
phase2_scales
command
Phase 2: Scales — Linear, Log10, Sqrt, Reverse, Discrete
|
Phase 2: Scales — Linear, Log10, Sqrt, Reverse, Discrete |
|
phase2_statistics
command
Phase 2: Statistics — Identity, Bin/Count, Density (KDE), Smooth (LOESS), Summary, BoxPlot
|
Phase 2: Statistics — Identity, Bin/Count, Density (KDE), Smooth (LOESS), Summary, BoxPlot |
|
phase4_pipeline
command
Phase 4 Pipeline: System Columns (PANEL, group) & Position Adjustments
|
Phase 4 Pipeline: System Columns (PANEL, group) & Position Adjustments |
|
phase5_transforms
command
Phase 5: Composable Stat Transforms — Filter, Sort, Group, Normalize, Stack, TopN, Select, Ribbon, Difference
|
Phase 5: Composable Stat Transforms — Filter, Sort, Group, Normalize, Stack, TopN, Select, Ribbon, Difference |
|
reference_lines
command
Reference Lines — HLine, VLine, and ABLine examples.
|
Reference Lines — HLine, VLine, and ABLine examples. |
|
scale_config
command
Phase 5a: Scale Configuration — Breaks, Labels, Formatter, Expand, MinorBreaks, and ClipBounds.
|
Phase 5a: Scale Configuration — Breaks, Labels, Formatter, Expand, MinorBreaks, and ClipBounds. |
|
showcase
command
Example: Feature Showcase
|
Example: Feature Showcase |
|
tabular_figures
command
Tabular Figures Example
|
Tabular Figures Example |
|
themes
command
Example: Theme Showcase
|
Example: Theme Showcase |
|
Package facet splits a dataset into subsets for "small multiple" panel layouts.
|
Package facet splits a dataset into subsets for "small multiple" panel layouts. |
|
Package fonts provides a cross-platform, pure-Go typography subsystem.
|
Package fonts provides a cross-platform, pure-Go typography subsystem. |
|
Package geom provides geometry specifications for the Grammar of Graphics.
|
Package geom provides geometry specifications for the Grammar of Graphics. |
|
Package output provides rendering output abstractions for exporting and displaying plots.
|
Package output provides rendering output abstractions for exporting and displaying plots. |
|
Package scale provides scale transformations that map data values to visual aesthetic values.
|
Package scale provides scale transformations that map data values to visual aesthetic values. |
|
Package stat provides composable statistical transforms for the Grammar of Graphics.
|
Package stat provides composable statistical transforms for the Grammar of Graphics. |
|
Package theme provides visual styling configurations for plots.
|
Package theme provides visual styling configurations for plots. |








