ggsql

researchposit-dev

Write ggsql queries — a grammar of graphics for SQL. Use when the user wants to create, modify, or understand a ggsql visualization query.

Install

npx skills add https://github.com/posit-dev/skills --skill ggsql

SKILL.md

---name: ggsqldescription: Write ggsql queries — a grammar of graphics for SQL. Use when the user wants to create, modify, or understand a ggsql visualization query.allowed-tools: Bash(ggsql:*)metadata: author: George Stagg (@georgestagg)version: 1.1license: MIT---

ggsql Query Writer

ggsql combines a SQL query with a Grammar-of-Graphics visualization spec in one syntax. Write queries using ONLY the syntax below — NEVER invent clauses, settings, aesthetics, layer types, or palette names; say so if unsure whether something exists.

Query structure

Optional SQL part + required VISUALISE/VISUALIZE part.

SELECT → VISUALISE: last statement is a SELECT (bare, WITH...SELECT, set ops); its result feeds VISUALISE, which has no FROM.

SELECT name, score_a, score_b FROM 'dataset.csv' WHERE value > 50
VISUALISE score_a AS x, score_b AS y
[DRAW / PLACE / SCALE / FACET / PROJECT / LABEL clauses]

VISUALISE FROM: VISUALISE supplies its own source (table/file/CTE/built-in), no trailing SELECT.

WITH summary AS (SELECT category, COUNT(*) AS n FROM 'dataset.csv' GROUP BY category)
VISUALISE category AS x, n AS y FROM summary
DRAW bar

Data sources (in VISUALISE ... FROM or DRAW ... MAPPING ... FROM): unquoted table/CTE (FROM sales), quoted file path (FROM 'data.csv'), built-in dataset (FROM ggsql:penguins, FROM ggsql:airquality).

VISUALISE clause

Starts the viz; optional global mappings inherited by every layer.

VISUALISE <mapping>, ... FROM <data-source>

Mapping forms: explicit column AS aesthetic (e.g. revenue AS y); implicit column (name = aesthetic name); wildcard * (all matching columns); constant 'red' AS fill.

VISUALISE bill_len AS x, bill_dep AS y, species AS fill FROM ggsql:penguins
VISUALISE * FROM my_table

DRAW clause

Defines a layer; multiple DRAW stack bottom→top. All subclauses optional given global mappings/data.

DRAW <layer-type>
  MAPPING <mapping>, ... FROM <data-source>
  REMAPPING <stat-property> AS <aesthetic>, ...
  SETTING <param> => <value>, ...
  FILTER <condition>
  PARTITION BY <column>, ...
  ORDER BY <column>, ...

MAPPING — same forms as VISUALISE; merges with (layer wins over) global mappings, can add its own FROM. null blocks inheriting a global mapping: MAPPING null AS color.
REMAPPING — for stat layers (histogram, density, boxplot, violin, smooth, bar w/o y): maps a computed stat to an aesthetic, e.g. REMAPPING density AS y instead of a layer's default stat.
SETTING — literal aesthetic values or layer params (bypasses scales), e.g. SETTING size => 5, stroke => 'red'. Position adjustment: 'identity' (default, most layers), 'stack' (default bar/histogram/area), 'dodge' (default boxplot/violin), 'jitter'.
FILTER — SQL WHERE condition on layer data: FILTER sex = 'female' AND body_mass > 4000.
PARTITION BY — extra grouping columns beyond discrete mappings: PARTITION BY Month.
ORDER BY — record order, matters for path: ORDER BY timestamp.

Aggregate (a SETTING)

Collapses each group (PARTITION BY cols + discrete mappings) to one row, replacing numeric mappings with aggregated values. Layers: point line path bar area ribbon range segment rule text tile (not stat layers, which have their own).

SETTING aggregate => '<spec>'                -- single
SETTING aggregate => ('<spec>', '<spec>', …) -- list

Spec is untargeted '<func>' (every unmapped-target numeric aesthetic; ≤2 untargeted defaults — 1st for lower-side aesthetics x/xmin/etc + all non-range layers, 2nd for upper-side xend/xmax) or targeted '<aes>:<func>' (overrides untargeted for that aesthetic).

Functions — reductions: count sum prod min max range mid mean median geomean harmean rms sdev var iqr se p05–p95; positional (need upstream ORDER BY): first last diff; band <offset>±[<mult>]<expansion> e.g. 'mean+1.96sdev' (offsets: mean median geomean harmean rms sum prod min max mid p05–p95; expansions: sdev se var iqr range).

Explosion: targeting one aesthetic with multiple functions emits one row/function/group, tagged by a synthetic aggregate column — drive another aesthetic via REMAPPING aggregate AS <aes>. Equal-length exploded aesthetics run in lockstep; single-function targets repeat each row. Mixed lengths >1 error.

-- min/max envelope as two lines per group, coloured by function
DRAW line MAPPING Date AS x, Temp AS y
  REMAPPING aggregate AS color
  SETTING aggregate => ('y:min', 'y:max')
  PARTITION BY Year

Scale interaction: for a targeted aesthetic, SCALE BINNED runs after aggregation (so stats aren't cancelled within a bin); untargeted SCALE BINNED still bins pre-aggregate to drive grouping. Continuous censoring (SCALE <aes> FROM (lo, hi)) and discrete OOB filtering defer to post-aggregate whenever that aesthetic is aggregated.

PLACE clause

Annotation layer, literal values only, no data mapping; tuples for multiple annotations.

PLACE point SETTING x => 5, y => 10, color => 'red'
PLACE text SETTING x => (34, 44), y => (66, 49), label => ('Mean = 34', 'Mean = 44')

SCALE clause

Maps data → aesthetic output; sensible defaults always apply. Only aesthetic is required.

SCALE <type> <aesthetic> FROM <input-range> TO <output-range> VIA <transform>
  SETTING <param> => <value>, ...
  RENAMING <value> => <label>, ...

Type (before aesthetic; inferred if omitted): CONTINUOUS, DISCRETE, BINNED (bin continuous→discrete, never auto), ORDINAL (never auto), IDENTITY (pass through, no legend).
Aesthetic — base name only: x y fill stroke color(=fill+stroke) opacity size linewidth linetype shape panel row column. Position families (xmin/xmax/xend/ymin/ymax/yend) scale via base name (SCALE x ...).
FROM — continuous (min, max), null infers ((0, null)); discrete ('A','B','C') sets order & nulls the rest, or include null explicitly.
TO — value array (('red','blue'), (1, 6)) or named palette (viridis, dark2, tableau10).
VIA — continuous: linear log log2 ln exp10 exp2 exp sqrt square asinh pseudo_log pseudo_log2 pseudo_ln integer; temporal (auto for date/datetime/time cols): date datetime time; discrete: string bool.
SETTING — continuous/binned: expand (factor or (mult,add), default 0.05, x/y only), oob ('keep' default x/y, 'censor' default others, 'squish'), breaks (count/array/interval string e.g. '2 months'), pretty (bool, default true), reverse (bool). Continuous only: minor_breaks (count/array/interval string; ignored by Vega-Lite). Binned only: closed ('left'/'right'). Discrete/ordinal: reverse.
RENAMING — direct + wildcard formatting (direct wins): RENAMING 'Adelie' => 'Pygoscelis adeliae', 'adelie' => null or RENAMING * => '{:Title}' (formatters: Title UPPER lower, time %B %Y, num %.1f).

SCALE x VIA date SETTING breaks => '2 months'
SCALE y FROM (0, 100) SETTING oob => 'squish'
SCALE BINNED x SETTING breaks => 10, pretty => false

FACET clause

Small multiples. 1D FACET region (wrap, aesthetic panel); 2D FACET region BY category (grid, aesthetics row/column). Settings: free (null default/fixed, 'x', 'y', ('x','y')), missing ('repeat' default / 'null'), ncol/nrow (1D only, pick one). Customize/filter via SCALE on the facet aesthetic:

FACET region
SCALE panel RENAMING 'N' => 'North', 'S' => 'South'
FACET island
SCALE panel FROM ('Biscoe', 'Dream')   -- filters panels shown

PROJECT clause

Coordinate system.

PROJECT <aesthetic>, ... TO <coord-type> SETTING <param> => <value>, ...

cartesian (default): aesthetics x/y; settings clip (bool, default true), ratio (number or null). polar: aesthetics radius(primary)/angle(secondary); settings clip, start/end (degrees, default 0/start+360), inner (0-1 donut hole, default 0). Swap order to flip axes (PROJECT y, x TO cartesian); without PROJECT, type is inferred from mappings.

PROJECT TO polar SETTING inner => 0.5   -- donut chart

LABEL clause

Overrides axis/legend labels & titles: title, subtitle, caption, or any aesthetic name; null suppresses.

LABEL title => 'Sales by Region', x => 'Date', y => 'Revenue (USD)', fill => null

Layer types

point — required x, y; optional size, colour, stroke, fill, opacity, shape.
line — required x, y; sorted by primary axis; optional colour/stroke, opacity, linewidth, linetype; settings position, orientation ('aligned'/'transposed').
path — like line but data-order (unsorted); same aesthetics.
bar — auto-counts if no y; optional x, y, fill, colour, stroke; stats count, proportion; property weight; settings position (default 'stack'), width. Orientation from mapping (x=vertical, y=horizontal).
histogram — required x; stats count, density (default remap count AS <secondary>); settings position ('stack'), bins (30), binwidth, closed.
density — required x; stats density, intensity; settings position ('identity'), bandwidth, adjust (1), kernel ('gaussian' default, epanechnikov triangular rectangular biweight cosine).
boxplot — required x (cat), y (cont); stats type, value; settings position ('dodge'), outliers (true), coef (1.5), width (0.9), hinge (points, default null/hidden).
violin — required x (cat), y (cont); stats density, intensity (default remap density AS offset); settings position ('dodge'), bandwidth, adjust, kernel, width (0.9), side ('both' 'left' 'bottom' 'right' 'top'), tails (default 3).
smooth — required x, y; stat intensity; settings method ('nw' default, 'ols', 'tls'), bandwidth, adjust, kernel (nw only).
area — required x, y, anchored at zero; settings position ('stack'), orientation, total (normalize), center (steamgraph).
ribbon — like area but explicit ymin/ymax, unanchored.
segment — required x, y, xend, yend; use range instead when one coord is shared between start/end.
rule — required x or y (full-panel reference line); optional slope (diagonal: y = a + slope*x).
text — required x, y, label; settings offset (number or (h,v)), format (RENAMING-style interpolation), parse (bool, default true: markdown **bold**/*italic*/~~strike~~/`code`/{.red span}; not in Vega-Lite), hjust ('left' 'right' 'centre' or 0-1), vjust ('top' 'bottom' 'middle' or 0-1).
rect — pick 2 per axis from center/min/max/width/height, or just center (defaults size to 1).
polygon — required x, y; ordered coords; PARTITION BY separates distinct polygons.
range — required x, ymin, ymax; setting hinge (points, default 10, null hides).

All layers accept colour/stroke, fill, opacity, linewidth, linetype, and position where applicable.

Named color palettes

Discrete: ggsql10(default) tableau10 category10 set1 set2 set3 dark2 paired pastel1 pastel2 accent kelly22
Sequential: sequential(default) viridis plasma magma inferno cividis blues greens oranges reds purples greys ylgnbu ylorbr ylorrd batlow hawaii lajolla turku …
Diverging: vik/diverging rdbu rdylbu rdylgn spectral brbg prgn piyg puor berlin roma …
Cyclic: romao/cyclic bamo broco corko viko

Common patterns

-- Pie chart: bar layer in polar coords
VISUALISE species AS fill FROM ggsql:penguins
DRAW bar
PROJECT TO polar

-- Multi-series line chart
VISUALISE Date AS x
DRAW line MAPPING Temp AS y, 'Temperature' AS color
DRAW line MAPPING Ozone AS y, 'Ozone' AS color
SCALE x VIA date

-- Lollipop chart
SELECT ROUND(bill_dep) AS bill_dep, COUNT(*) AS n FROM ggsql:penguins GROUP BY 1
VISUALISE bill_dep AS x
DRAW range MAPPING 0 AS ymin, n AS ymax SETTING hinge => null
DRAW point MAPPING n AS y

-- Ridgeline / joy plot
VISUALISE Temp AS x, Month AS y FROM ggsql:airquality
DRAW violin SETTING width => 4, side => 'top'
SCALE ORDINAL y

-- Mean ± 1.96·sdev band per group, as a ribbon
VISUALISE Day AS x, Temp AS ymin, Temp AS ymax FROM ggsql:airquality
DRAW ribbon SETTING aggregate => ('mean-1.96sdev', 'mean+1.96sdev') PARTITION BY Month

CLI

ggsql subcommands: exec <QUERY>, run <FILE>, validate <QUERY>, parse <QUERY>, view <QUERY> (window, blocks until closed). Options: --reader <URI> (default duckdb://memory), --writer <FORMAT> (default vegalite), --output <PATH> (extension picks writer), -D key=value, -v. Writers: vegalite svg pdf hep (no GPU) and png jpeg tiff webp (GPU, not every build).

Don't run ggsql view unless a window was requested — it blocks and you can't close it; use --output instead. Prefer svg/pdf for pictures (no GPU adapter needed); ggsql exec --help lists available writers.

ggsql exec "VISUALISE bill_len AS x, bill_dep AS y FROM ggsql:penguins DRAW point" -v
ggsql exec "VISUALISE species AS fill FROM ggsql:penguins DRAW bar" -o chart.svg

Reference

https://ggsql.org/syntax/index.llms.md — latest syntax docs.

Instructions for responding

Write a complete, valid ggsql query for the request; use SQL/CTEs before VISUALISE for data shaping.
Choose the simplest layer types/settings that work; add SCALE for formatting/palettes/ranges and LABEL for titles when warranted.
Briefly explain your choices after the query. Never invent syntax — say so if unsure.
Default to ggsql:penguins/ggsql:airquality when no data is specified.
Use ggsql validate "<query>" to validate, ggsql exec "<query>" -v to run and show output.