ggplot_rs/geom/
density.rs

1use crate::aes::Aesthetic;
2use crate::coord::Coord;
3use crate::data::{DataFrame, Value};
4use crate::position::identity::PositionIdentity;
5use crate::position::Position;
6use crate::render::backend::{DrawBackend, LineStyle, Linetype, PointShape, PointStyle, RectStyle};
7use crate::render::RenderError;
8use crate::scale::ScaleSet;
9use crate::stat::density::StatDensity;
10use crate::stat::Stat;
11use crate::theme::Theme;
12
13use super::{Geom, GeomParams};
14
15/// Density curve geometry — filled area under a kernel density estimate.
16pub struct GeomDensity {
17    pub fill: (u8, u8, u8),
18    pub color: (u8, u8, u8),
19    pub alpha: f64,
20    pub line_width: f64,
21}
22
23impl Default for GeomDensity {
24    fn default() -> Self {
25        GeomDensity {
26            fill: (97, 156, 255),
27            color: (50, 50, 50),
28            alpha: 0.3,
29            line_width: 1.0,
30        }
31    }
32}
33
34impl Geom for GeomDensity {
35    fn draw(
36        &self,
37        data: &DataFrame,
38        coord: &dyn Coord,
39        scales: &ScaleSet,
40        _theme: &Theme,
41        backend: &mut dyn DrawBackend,
42    ) -> Result<(), RenderError> {
43        let x_col = data
44            .column("x")
45            .ok_or(RenderError::MissingAesthetic("x".into()))?;
46        let y_col = data
47            .column("y")
48            .ok_or(RenderError::MissingAesthetic("y".into()))?;
49        let fill_col = data.column("fill");
50        let color_col = data.column("color");
51
52        let plot_area = backend.plot_area();
53        let x_scale = scales.get(&Aesthetic::X);
54        let y_scale = scales.get(&Aesthetic::Y);
55
56        let base_ny = y_scale.map(|s| s.map(&Value::Float(0.0))).unwrap_or(0.0);
57
58        // Determine groups from color or fill column
59        let group_col = color_col.or(fill_col);
60        let groups: Vec<(String, Vec<usize>)> = if let Some(gc) = group_col {
61            let mut groups: Vec<(String, Vec<usize>)> = Vec::new();
62            for (i, v) in gc.iter().enumerate() {
63                let key = v.to_group_key();
64                if let Some(entry) = groups.iter_mut().find(|(k, _)| k == &key) {
65                    entry.1.push(i);
66                } else {
67                    groups.push((key, vec![i]));
68                }
69            }
70            groups
71        } else {
72            // Single group with all indices
73            vec![("".to_string(), (0..data.nrows()).collect())]
74        };
75
76        for (group_label, indices) in &groups {
77            if indices.is_empty() {
78                continue;
79            }
80            let first_idx = indices[0];
81
82            // Resolve fill: use fill scale if fill column exists, else use color scale, else default
83            let fill_color = fill_col
84                .and_then(|fc| scales.map_color(&Aesthetic::Fill, &fc[first_idx]))
85                .or_else(|| {
86                    color_col.and_then(|cc| scales.map_color(&Aesthetic::Color, &cc[first_idx]))
87                })
88                .unwrap_or(self.fill);
89
90            // Resolve line: use color scale if color column exists, else use fill scale, else default
91            let line_color = color_col
92                .and_then(|cc| scales.map_color(&Aesthetic::Color, &cc[first_idx]))
93                .or_else(|| {
94                    fill_col.and_then(|fc| scales.map_color(&Aesthetic::Fill, &fc[first_idx]))
95                })
96                .unwrap_or(self.color);
97
98            let mut upper: Vec<(f64, f64)> = Vec::new();
99            let mut lower: Vec<(f64, f64)> = Vec::new();
100
101            for &i in indices {
102                let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
103                let ny = y_scale.map(|s| s.map(&y_col[i])).unwrap_or(0.0);
104                upper.push(coord.transform((nx, ny), &plot_area));
105                lower.push(coord.transform((nx, base_ny), &plot_area));
106            }
107
108            // Filled polygon
109            let mut polygon = upper.clone();
110            lower.reverse();
111            polygon.extend(lower);
112
113            if polygon.len() >= 3 {
114                backend.draw_polygon(
115                    &polygon,
116                    &RectStyle {
117                        fill: Some(fill_color),
118                        stroke: None,
119                        stroke_width: 0.0,
120                        alpha: self.alpha,
121                        clip: true,
122                    },
123                )?;
124            }
125
126            // Top line
127            if upper.len() >= 2 {
128                backend.draw_line(
129                    &upper,
130                    &LineStyle {
131                        color: line_color,
132                        alpha: 1.0,
133                        width: self.line_width,
134                        linetype: Linetype::Solid,
135                        ..Default::default()
136                    },
137                )?;
138            }
139
140            // Sparse invisible hover points: the curve carries no marks, so emit a
141            // handful of transparent points along it (tagged with the x value and
142            // density) for the axis-pointer to read on hover.
143            let step = (indices.len() / 48).max(1);
144            for (k, &i) in indices.iter().enumerate() {
145                if k % step != 0 {
146                    continue;
147                }
148                let dens = y_col[i]
149                    .as_f64()
150                    .map(|f| format!("{f:.4}"))
151                    .unwrap_or_default();
152                let tip = if group_label.is_empty() {
153                    format!("density: {dens}")
154                } else {
155                    format!("{group_label}: {dens}")
156                };
157                super::set_mark(
158                    backend,
159                    Some(tip),
160                    Some(super::tip_value(&x_col[i])),
161                    super::series_key(data, i),
162                    super::measured_value(data, i),
163                );
164                super::set_mark_formatted(
165                    backend,
166                    scales,
167                    Some(&x_col[i]),
168                    &Aesthetic::Y,
169                    super::measured_raw(data, i),
170                );
171                backend.draw_shape(
172                    upper[k],
173                    0.6,
174                    &PointStyle {
175                        color: line_color,
176                        alpha: 0.0,
177                        filled: true,
178                        shape: PointShape::Circle,
179                    },
180                )?;
181            }
182            super::clear_mark(backend);
183        }
184
185        Ok(())
186    }
187
188    fn required_aes(&self) -> Vec<Aesthetic> {
189        vec![Aesthetic::X]
190    }
191
192    fn default_stat(&self) -> Box<dyn Stat> {
193        Box::new(StatDensity::default())
194    }
195
196    fn default_position(&self) -> Box<dyn Position> {
197        Box::new(PositionIdentity)
198    }
199
200    fn default_params(&self) -> GeomParams {
201        GeomParams::default()
202    }
203
204    fn name(&self) -> &str {
205        "density"
206    }
207
208    fn set_series_color(&mut self, color: (u8, u8, u8)) {
209        self.fill = color;
210    }
211}
ggplot_rs/geom/density.rs

ggplot_rs/geom/
density.rs
