add side to jitter and boxplot (#439)

Author: thomasp85

CHANGELOG.md

@@ -5,9 +5,17 @@
 - New `aggregate` SETTING on Identity-stat layers (point, line, area, bar, ribbon,
   range, segment, arrow, rule, text). By default it collapses each group to a
   single row by replacing every numeric mapping in place with its aggregated
-  value. See the `DRAW` documentation for details.
+  value. See the `DRAW` documentation for details (#384).
 - Added panel decorations (grid lines, axes, background) for polar coordinates (#156).
 - Added `radar` setting to polar coordinates for making radar plots (#418).
+- New `side` SETTING on the `boxplot` layer and the `jitter` position, mirroring
+  the existing `violin` setting (#439).
+
+### Fixed
+
+- Dodging of horizontal violin plots were broken due to a bad orientation
+  assumption in the VegaLite writer. We now correctly use the orientation to
+  dodge in the correct dimension (#439).
 
 ## 0.3.2 - 2026-05-05
 

doc/syntax/layer/position/jitter.qmd

@@ -23,6 +23,12 @@ Apart from the settings of the layer type, setting `position => 'jitter'` will a
   If `distribution` is either `'density'` or `'intensity'` then one of the axes must be continuous
 * `bandwidth`: Smoothing bandwidth for the `'density'` and `'intensity'` distributions (must be > 0). If absent (default), the bandwidth will be computed using Silverman's rule of thumb.
 * `adjust`: Multiplier for the `bandwidth` setting (must be > 0). Defaults to 1.
+* `side`: Constrains the jitter to one side of the original position by folding the sample into half of the width. Dodge centers and per-group widths are computed from the full `width`, so a one-sided jitter sits inside half of the same allocated band that a two-sided jitter would fill — pairing cleanly with a half-violin or half-boxplot on the other side. One of:
+    * `'both'` (default) jitters in both directions equally.
+    * `'left'` or `'bottom'` jitters only toward negative offsets.
+    * `'right'` or `'top'` jitters only toward positive offsets.
+
+  When both axes are jittered, `side` applies independently to each axis (e.g. `'right'` produces non-negative offsets on both axes).
 
 ## Examples
 When plotting points on a discrete axis they are all placed in the middle
@@ -65,3 +71,11 @@ DRAW point
 SCALE BINNED fill
   SETTING breaks => 4, pretty => false
 ```
+
+Pair a half-violin with one-sided jittered points by setting opposite `side` values:
+
+```{ggsql}
+VISUALISE species AS x, bill_dep AS y FROM ggsql:penguins
+DRAW violin SETTING side => 'left'
+DRAW point SETTING position => 'jitter', side => 'right', width => 0.4
+```

doc/syntax/layer/type/boxplot.qmd

@@ -27,6 +27,10 @@ The following aesthetics are recognised by the boxplot layer.
 * `outliers`: Whether to display outliers as points. Defaults to `true`.
 * `coef`: Length of the whiskers as a multiple of the IQR (must be >= 0). Defaults to `1.5`.
 * `width`: Relative width of the boxes (0 to 1). Defaults to `0.9`.
+* `side`: Determines the sides of the centerline where the box is displayed. Only the box and median tick shift to the chosen side; whiskers and outliers remain on the centerline. The full `width` is preserved for dodge calculations, so a half-box pairs cleanly with a half-violin or one-sided jitter on the same band. One of:
+    * `'both'` (default) displays a complete box on both sides of the centerline.
+    * `'left'` or `'bottom'` displays only the half-box on the left side or bottom side.
+    * `'right'` or `'top'` displays only the half-box on the right side or top side.
 
 ## Data transformation
 Per group, data will be divided into 4 quartiles and summary statistics will be derived from their extremes. 
@@ -91,3 +95,11 @@ VISUALISE FROM ggsql:penguins
 DRAW boxplot
   MAPPING species AS y, bill_len AS x
 ```
+
+Pair a half-violin with a half-boxplot on the same category by setting opposite `side` values:
+
+```{ggsql}
+VISUALISE bill_len AS x, species AS y FROM ggsql:penguins
+DRAW violin SETTING side => 'top'
+DRAW boxplot SETTING side => 'bottom', width => 0.3
+```

doc/syntax/layer/type/violin.qmd

@@ -117,4 +117,16 @@ To achieve this outcome, you can set the `side` setting and adjust `width` to ta
 VISUALISE Temp AS x, Month AS y FROM ggsql:airquality
 DRAW violin SETTING width => 4, side => 'top'
 SCALE ORDINAL y
-```
+```
+
+The same facilities can be used to create violins where each side encode different subsets
+
+```{ggsql}
+VISUALISE body_mass AS y, species AS x, sex AS fill FROM ggsql:penguins
+DRAW violin
+  SETTING side => 'left'
+  FILTER sex = 'male'
+DRAW violin
+  SETTING side => 'right'
+  FILTER sex = 'female'
+```

src/plot/layer/geom/boxplot.rs

@@ -2,7 +2,7 @@
 
 use std::collections::HashMap;
 
-use super::types::POSITION_VALUES;
+use super::types::{POSITION_VALUES, SIDE_VALUES};
 use super::{DefaultAesthetics, GeomTrait, GeomType};
 use crate::{
     naming,
@@ -72,6 +72,11 @@ impl GeomTrait for Boxplot {
                 default: DefaultParamValue::String("dodge"),
                 constraint: ParamConstraint::string_option(POSITION_VALUES),
             },
+            ParamDefinition {
+                name: "side",
+                default: DefaultParamValue::String("both"),
+                constraint: ParamConstraint::string_option(SIDE_VALUES),
+            },
         ];
         PARAMS
     }
@@ -539,7 +544,7 @@ mod tests {
         let boxplot = Boxplot;
         let params = boxplot.default_params();
 
-        assert_eq!(params.len(), 4);
+        assert_eq!(params.len(), 5);
 
         // Find and verify outliers param
         let outliers_param = params.iter().find(|p| p.name == "outliers").unwrap();
@@ -566,6 +571,13 @@ mod tests {
             position_param.default,
             DefaultParamValue::String("dodge")
         ));
+
+        // Find and verify side param (defaults to both)
+        let side_param = params.iter().find(|p| p.name == "side").unwrap();
+        assert!(matches!(
+            side_param.default,
+            DefaultParamValue::String("both")
+        ));
     }
 
     #[test]

src/plot/layer/geom/types.rs

@@ -18,6 +18,11 @@ pub const POSITION_VALUES: &[&str] = &["identity", "stack", "dodge", "jitter"];
 /// Closed interval side values for binned data
 pub const CLOSED_VALUES: &[&str] = &["left", "right"];
 
+/// Standard `side` parameter values for layers and positions that can render
+/// either both halves of a symmetric shape (or jitter range) or just one of
+/// them. Used by violin, boxplot, and jitter.
+pub const SIDE_VALUES: &[&str] = &["both", "left", "top", "right", "bottom"];
+
 /// Aesthetic aliases: user-facing names that resolve to concrete aesthetics.
 ///
 /// An alias is considered supported if any of its target aesthetics are supported

src/plot/layer/geom/violin.rs

@@ -1,6 +1,6 @@
 //! Violin geom implementation
 
-use super::types::POSITION_VALUES;
+use super::types::{POSITION_VALUES, SIDE_VALUES};
 use super::{DefaultAesthetics, GeomTrait, GeomType, StatResult};
 use crate::{
     naming,
@@ -24,8 +24,6 @@ const KERNEL_VALUES: &[&str] = &[
     "cosine",
 ];
 
-const SIDE_VALUES: &[&str] = &["both", "left", "top", "right", "bottom"];
-
 /// Violin geom - violin plots (mirrored density)
 #[derive(Debug, Clone, Copy)]
 pub struct Violin;