ggplot_rs/geom/
smooth.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::smooth::{SmoothMethod, StatSmooth};
10use crate::stat::Stat;
11use crate::theme::Theme;
12
13use super::{Geom, GeomParams};
14
15/// Smooth line with optional confidence ribbon.
16pub struct GeomSmooth {
17    pub color: (u8, u8, u8),
18    pub fill: (u8, u8, u8),
19    pub line_width: f64,
20    pub alpha: f64,
21    pub se: bool,
22    pub n_points: usize,
23    pub method: SmoothMethod,
24}
25
26impl Default for GeomSmooth {
27    fn default() -> Self {
28        GeomSmooth {
29            color: (51, 102, 204),
30            fill: (51, 102, 204),
31            line_width: 1.5,
32            alpha: 0.2,
33            se: true,
34            n_points: 80,
35            method: SmoothMethod::Lm,
36        }
37    }
38}
39
40impl GeomSmooth {
41    /// Use LOESS smoothing with the given span.
42    pub fn loess(mut self, span: f64) -> Self {
43        self.method = SmoothMethod::Loess { span };
44        self
45    }
46
47    /// Use penalized B-spline (P-spline) GAM smoothing — ggplot2's
48    /// `method = "gam"`, backed by anofox-regression with GCV-selected λ.
49    #[cfg(feature = "regression")]
50    pub fn gam(mut self) -> Self {
51        self.method = SmoothMethod::Gam;
52        self
53    }
54
55    /// Use a generalized linear model — ggplot2's
56    /// `geom_smooth(method = "glm", method.args = list(family = …))` — e.g.
57    /// `GeomSmooth::default().glm(SmoothFamily::binomial())`. The band is the
58    /// link-scale confidence interval mapped through the inverse link (see
59    /// [`SmoothFamily`](crate::stat::smooth::SmoothFamily)).
60    #[cfg(feature = "regression")]
61    pub fn glm(mut self, family: crate::stat::smooth::SmoothFamily) -> Self {
62        self.method = SmoothMethod::Glm { family };
63        self
64    }
65}
66
67impl Geom for GeomSmooth {
68    fn draw(
69        &self,
70        data: &DataFrame,
71        coord: &dyn Coord,
72        scales: &ScaleSet,
73        _theme: &Theme,
74        backend: &mut dyn DrawBackend,
75    ) -> Result<(), RenderError> {
76        let x_col = data
77            .column("x")
78            .ok_or(RenderError::MissingAesthetic("x".into()))?;
79        let y_col = data
80            .column("y")
81            .ok_or(RenderError::MissingAesthetic("y".into()))?;
82        let ymin_col = data.column("ymin");
83        let ymax_col = data.column("ymax");
84        let color_col = data.column("color");
85        let fill_col = data.column("fill");
86
87        let plot_area = backend.plot_area();
88        let x_scale = scales.get(&Aesthetic::X);
89        let y_scale = scales.get(&Aesthetic::Y);
90
91        // If there's a color/fill aesthetic, draw separate smooths per group
92        if let Some(cc) = color_col.or(fill_col) {
93            let mut groups: Vec<(String, Vec<usize>)> = Vec::new();
94            for (i, v) in cc.iter().enumerate() {
95                let key = v.to_group_key();
96                if let Some(entry) = groups.iter_mut().find(|(k, _)| k == &key) {
97                    entry.1.push(i);
98                } else {
99                    groups.push((key, vec![i]));
100                }
101            }
102
103            for (_, indices) in &groups {
104                let first_idx = indices[0];
105
106                // Determine colors from mapped aesthetics
107                let line_color = color_col
108                    .and_then(|c| scales.map_color(&Aesthetic::Color, &c[first_idx]))
109                    .unwrap_or(self.color);
110                let ribbon_fill = fill_col
111                    .and_then(|f| scales.map_color(&Aesthetic::Fill, &f[first_idx]))
112                    .or_else(|| {
113                        color_col.and_then(|c| scales.map_color(&Aesthetic::Color, &c[first_idx]))
114                    })
115                    .unwrap_or(self.fill);
116
117                // Draw confidence ribbon
118                if self.se {
119                    if let (Some(ymin), Some(ymax)) = (ymin_col, ymax_col) {
120                        let mut upper_points: Vec<(f64, f64)> = Vec::new();
121                        let mut lower_points: Vec<(f64, f64)> = Vec::new();
122
123                        for &i in indices {
124                            let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
125                            let ny_max = y_scale.map(|s| s.map(&ymax[i])).unwrap_or(0.0);
126                            let ny_min = y_scale.map(|s| s.map(&ymin[i])).unwrap_or(0.0);
127
128                            upper_points.push(coord.transform((nx, ny_max), &plot_area));
129                            lower_points.push(coord.transform((nx, ny_min), &plot_area));
130                        }
131
132                        let mut polygon = upper_points;
133                        lower_points.reverse();
134                        polygon.extend(lower_points);
135
136                        if polygon.len() >= 3 {
137                            backend.draw_polygon(
138                                &polygon,
139                                &RectStyle {
140                                    fill: Some(ribbon_fill),
141                                    stroke: None,
142                                    stroke_width: 0.0,
143                                    alpha: self.alpha,
144                                    clip: true,
145                                },
146                            )?;
147                        }
148                    }
149                }
150
151                // Draw fitted line
152                let points: Vec<(f64, f64)> = indices
153                    .iter()
154                    .map(|&i| {
155                        let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
156                        let ny = y_scale.map(|s| s.map(&y_col[i])).unwrap_or(0.0);
157                        coord.transform((nx, ny), &plot_area)
158                    })
159                    .collect();
160
161                if points.len() >= 2 {
162                    backend.draw_line(
163                        &points,
164                        &LineStyle {
165                            color: line_color,
166                            alpha: 1.0,
167                            width: self.line_width,
168                            linetype: Linetype::Solid,
169                            ..Default::default()
170                        },
171                    )?;
172                    draw_hover_marks(
173                        backend, scales, &points, indices, x_col, y_col, ymin_col, ymax_col,
174                        line_color,
175                    )?;
176                }
177            }
178        } else {
179            // No grouping — original behavior with fixed colors
180
181            // Draw confidence ribbon first (behind line)
182            if self.se {
183                if let (Some(ymin), Some(ymax)) = (ymin_col, ymax_col) {
184                    let mut upper_points: Vec<(f64, f64)> = Vec::new();
185                    let mut lower_points: Vec<(f64, f64)> = Vec::new();
186
187                    for i in 0..data.nrows() {
188                        let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
189                        let ny_max = y_scale.map(|s| s.map(&ymax[i])).unwrap_or(0.0);
190                        let ny_min = y_scale.map(|s| s.map(&ymin[i])).unwrap_or(0.0);
191
192                        upper_points.push(coord.transform((nx, ny_max), &plot_area));
193                        lower_points.push(coord.transform((nx, ny_min), &plot_area));
194                    }
195
196                    // Build polygon: upper left-to-right, then lower right-to-left
197                    let mut polygon = upper_points;
198                    lower_points.reverse();
199                    polygon.extend(lower_points);
200
201                    if polygon.len() >= 3 {
202                        backend.draw_polygon(
203                            &polygon,
204                            &RectStyle {
205                                fill: Some(self.fill),
206                                stroke: None,
207                                stroke_width: 0.0,
208                                alpha: self.alpha,
209                                clip: true,
210                            },
211                        )?;
212                    }
213                }
214            }
215
216            // Draw fitted line
217            let points: Vec<(f64, f64)> = (0..data.nrows())
218                .map(|i| {
219                    let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
220                    let ny = y_scale.map(|s| s.map(&y_col[i])).unwrap_or(0.0);
221                    coord.transform((nx, ny), &plot_area)
222                })
223                .collect();
224
225            if points.len() >= 2 {
226                backend.draw_line(
227                    &points,
228                    &LineStyle {
229                        color: self.color,
230                        alpha: 1.0,
231                        width: self.line_width,
232                        linetype: Linetype::Solid,
233                        ..Default::default()
234                    },
235                )?;
236                let rows: Vec<usize> = (0..data.nrows()).collect();
237                draw_hover_marks(
238                    backend, scales, &points, &rows, x_col, y_col, ymin_col, ymax_col, self.color,
239                )?;
240            }
241        }
242
243        Ok(())
244    }
245
246    fn required_aes(&self) -> Vec<Aesthetic> {
247        vec![Aesthetic::X, Aesthetic::Y]
248    }
249
250    fn default_stat(&self) -> Box<dyn Stat> {
251        Box::new(StatSmooth {
252            n_points: self.n_points,
253            se: self.se,
254            method: self.method.clone(),
255        })
256    }
257
258    fn default_position(&self) -> Box<dyn Position> {
259        Box::new(PositionIdentity)
260    }
261
262    fn default_params(&self) -> GeomParams {
263        GeomParams::default()
264    }
265
266    fn name(&self) -> &str {
267        "smooth"
268    }
269
270    fn apply_element_geom(&mut self, el: &crate::theme::elements::ElementGeom) {
271        const DEFAULT: (u8, u8, u8) = (51, 102, 204);
272        if let (true, Some(accent)) = (self.color == DEFAULT, el.accent) {
273            self.color = accent;
274        }
275        if let (true, Some(accent)) = (self.fill == DEFAULT, el.accent) {
276            self.fill = accent;
277        }
278    }
279
280    fn set_series_color(&mut self, color: (u8, u8, u8)) {
281        self.color = color;
282        self.fill = color;
283    }
284}
285
286/// The fitted curve is drawn as a single path and so carries no per-point
287/// marks. Emit a sparse set of transparent hover points along it — each tagged
288/// with the fitted `ŷ` (and the CI when present) — so the axis pointer can read
289/// the smoother on hover, mirroring `geom_density`.
290#[allow(clippy::too_many_arguments)]
291fn draw_hover_marks(
292    backend: &mut dyn DrawBackend,
293    scales: &ScaleSet,
294    points: &[(f64, f64)],
295    rows: &[usize],
296    x_col: &[Value],
297    y_col: &[Value],
298    ymin_col: Option<&[Value]>,
299    ymax_col: Option<&[Value]>,
300    color: (u8, u8, u8),
301) -> Result<(), RenderError> {
302    let step = (rows.len() / 40).max(1);
303    for (k, &i) in rows.iter().enumerate() {
304        if k % step != 0 {
305            continue;
306        }
307        super::set_mark(
308            backend,
309            Some(smooth_tip(y_col, ymin_col, ymax_col, i)),
310            Some(super::tip_value(&x_col[i])),
311            None,
312            super::raw_value(&y_col[i]),
313        );
314        super::set_mark_formatted(
315            backend,
316            scales,
317            Some(&x_col[i]),
318            &Aesthetic::Y,
319            Some(&y_col[i]),
320        );
321        backend.draw_shape(
322            points[k],
323            0.6,
324            &PointStyle {
325                color,
326                alpha: 0.0,
327                filled: true,
328                shape: PointShape::Circle,
329            },
330        )?;
331    }
332    super::clear_mark(backend);
333    Ok(())
334}
335
336/// `ŷ = <fitted>` plus ` [lo, hi]` when a confidence band is present.
337fn smooth_tip(
338    y_col: &[Value],
339    ymin_col: Option<&[Value]>,
340    ymax_col: Option<&[Value]>,
341    i: usize,
342) -> String {
343    let yv = y_col[i]
344        .as_f64()
345        .map(|f| format!("{f:.3}"))
346        .unwrap_or_default();
347    let ci = match (ymin_col, ymax_col) {
348        (Some(lo), Some(hi)) => match (lo[i].as_f64(), hi[i].as_f64()) {
349            (Some(a), Some(b)) => format!(" [{a:.3}, {b:.3}]"),
350            _ => String::new(),
351        },
352        _ => String::new(),
353    };
354    format!("ŷ = {yv}{ci}")
355}
ggplot_rs/geom/smooth.rs

ggplot_rs/geom/
smooth.rs
