ggplot_rs/geom/
histogram.rs

1use crate::aes::Aesthetic;
2use crate::coord::Coord;
3use crate::data::DataFrame;
4use crate::position::identity::PositionIdentity;
5use crate::position::Position;
6use crate::render::backend::{DrawBackend, RectStyle};
7use crate::render::RenderError;
8use crate::scale::ScaleSet;
9use crate::stat::bin::StatBin;
10use crate::stat::Stat;
11use crate::theme::Theme;
12
13use super::{Geom, GeomParams};
14
15/// Histogram geometry (bar chart with StatBin).
16pub struct GeomHistogram {
17    pub bins: usize,
18    pub binwidth: Option<f64>,
19    pub fill: (u8, u8, u8),
20    pub color: (u8, u8, u8),
21    pub alpha: f64,
22}
23
24impl GeomHistogram {
25    /// Set bin width (overrides bins count).
26    pub fn with_binwidth(mut self, width: f64) -> Self {
27        self.binwidth = Some(width);
28        self
29    }
30
31    /// Set number of bins.
32    pub fn with_bins(mut self, bins: usize) -> Self {
33        self.bins = bins;
34        self.binwidth = None;
35        self
36    }
37}
38
39impl Default for GeomHistogram {
40    fn default() -> Self {
41        GeomHistogram {
42            bins: 30,
43            binwidth: None,
44            fill: (97, 156, 255),
45            color: (50, 50, 50),
46            alpha: 1.0,
47        }
48    }
49}
50
51impl Geom for GeomHistogram {
52    fn draw(
53        &self,
54        data: &DataFrame,
55        coord: &dyn Coord,
56        scales: &ScaleSet,
57        _theme: &Theme,
58        backend: &mut dyn DrawBackend,
59    ) -> Result<(), RenderError> {
60        let xmin_col = data.column("xmin");
61        let xmax_col = data.column("xmax");
62        let y_col = data
63            .column("y")
64            .ok_or(RenderError::MissingAesthetic("y".into()))?;
65
66        let plot_area = backend.plot_area();
67        let x_scale = scales.get(&Aesthetic::X);
68        let y_scale = scales.get(&Aesthetic::Y);
69
70        for i in 0..data.nrows() {
71            let (left_n, right_n) = match (xmin_col, xmax_col) {
72                (Some(xmin), Some(xmax)) => {
73                    let ln = x_scale.map(|s| s.map(&xmin[i])).unwrap_or(0.0);
74                    let rn = x_scale.map(|s| s.map(&xmax[i])).unwrap_or(1.0);
75                    (ln, rn)
76                }
77                _ => {
78                    // Fall back to x column with small width
79                    let x_col = data
80                        .column("x")
81                        .ok_or(RenderError::MissingAesthetic("x".into()))?;
82                    let nx = x_scale.map(|s| s.map(&x_col[i])).unwrap_or(0.0);
83                    (nx - 0.02, nx + 0.02)
84                }
85            };
86
87            let ny = y_scale.map(|s| s.map(&y_col[i])).unwrap_or(0.0);
88            let ny_base = y_scale
89                .map(|s| s.map(&crate::data::Value::Float(0.0)))
90                .unwrap_or(0.0);
91
92            let (left_px, top_px) = coord.transform((left_n, ny), &plot_area);
93            let (right_px, bottom_px) = coord.transform((right_n, ny_base), &plot_area);
94
95            // Hover tooltip: the bin range and its count.
96            let cnt = super::tip_value(&y_col[i]);
97            let tip = match (xmin_col, xmax_col) {
98                (Some(lo), Some(hi)) => format!(
99                    "[{}, {}): {cnt}",
100                    super::tip_value(&lo[i]),
101                    super::tip_value(&hi[i])
102                ),
103                _ => format!("count: {cnt}"),
104            };
105            super::set_mark(
106                backend,
107                Some(tip),
108                data.column("x").map(|c| super::tip_value(&c[i])),
109                super::series_key(data, i),
110                super::measured_value(data, i),
111            );
112            super::set_row_extras(backend, data, i);
113
114            backend.draw_rect(
115                (left_px, top_px.min(bottom_px)),
116                (right_px, top_px.max(bottom_px)),
117                &RectStyle {
118                    fill: Some(self.fill),
119                    stroke: Some(self.color),
120                    stroke_width: 0.5,
121                    alpha: self.alpha,
122                    clip: true,
123                },
124            )?;
125        }
126        super::clear_mark(backend);
127        super::clear_row_extras(backend);
128
129        Ok(())
130    }
131
132    fn required_aes(&self) -> Vec<Aesthetic> {
133        vec![Aesthetic::X]
134    }
135
136    fn default_stat(&self) -> Box<dyn Stat> {
137        let mut stat = StatBin {
138            bins: self.bins,
139            binwidth: self.binwidth,
140        };
141        if let Some(bw) = self.binwidth {
142            stat = stat.with_binwidth(bw);
143        }
144        Box::new(stat)
145    }
146
147    fn default_position(&self) -> Box<dyn Position> {
148        Box::new(PositionIdentity)
149    }
150
151    fn default_params(&self) -> GeomParams {
152        GeomParams::default()
153    }
154
155    fn name(&self) -> &str {
156        "histogram"
157    }
158
159    fn include_zero_baseline(&self) -> bool {
160        true
161    }
162
163    fn set_series_color(&mut self, color: (u8, u8, u8)) {
164        self.fill = color;
165    }
166}
167
168#[cfg(test)]
169mod tests {
170    use crate::aes::{AesMapping, Aesthetic, MappingStage};
171    use crate::data::Value;
172    use crate::prelude::*;
173
174    /// Review R-7 (nit): an after_stat `data_attr` on a histogram — there's
175    /// no builder for it (`Aes::data_attr` only maps BeforeStat), so this
176    /// manually constructs the mapping, the same way a caller reaching for
177    /// R's `stage()`-equivalent would have to. It must actually work (the
178    /// underlying gap was `GeomHistogram` never calling
179    /// `geom::set_row_extras` at all, not anything specific to after_stat).
180    #[test]
181    fn after_stat_data_attr_works_on_a_histogram() {
182        let n = 50;
183        let x: Vec<Value> = (0..n).map(|i| Value::Float(i as f64 * 0.2)).collect();
184        let mut aes = Aes::new().x("x");
185        aes.mappings.push(AesMapping {
186            column: "count".to_string(),
187            aesthetic: Aesthetic::DataAttr("data-n".to_string()),
188            stage: MappingStage::AfterStat,
189        });
190
191        let svg = GGPlot::new(vec![("x".into(), x)])
192            .aes(aes)
193            .geom_histogram()
194            .render_svg_native_with_size(400, 300)
195            .unwrap();
196
197        assert!(svg.contains("data-n=\""));
198    }
199}
ggplot_rs/geom/histogram.rs

ggplot_rs/geom/
histogram.rs
