Function new

examples/heatmap.rs:24–73

()

}

fn new() -> PlotWidget {
    let cols = 40;
    let rows = 30;
    let mut positions = Vec::with_capacity(cols * rows);
    let mut values = Vec::with_capacity(cols * rows);

    for y in 0..rows {
        for x in 0..cols {
            let nx = x as f64 / (cols - 1) as f64;
            let ny = y as f64 / (rows - 1) as f64;
            let value = heat_value(nx, ny);
            positions.push([x as f64, y as f64]);
            values.push(value);
        }
    }

    let (min_value, max_value) = values.iter().fold((f64::MAX, f64::MIN), |acc, v| {
        (acc.0.min(*v), acc.1.max(*v))
    });
    let span = (max_value - min_value).max(1e-12);
    let colors = values
        .iter()
        .map(|v| heat_color((v - min_value) / span))
        .collect::<Vec<Color>>();

    let heatmap = Series::markers_only(positions, MarkerStyle::new_world(0.9, MarkerType::Square))
        .with_label("heatmap")
        .with_point_colors(colors);

    PlotWidgetBuilder::new()
        .add_series(heatmap)
        .with_x_label("X")
        .with_y_label("Y")
        .with_tick_label_size(12.0)
        .with_axis_label_size(18.0)
        .with_data_aspect(1.0) // keep the pixels square
        .with_hover_highlight_provider(move |_ctx, point| {
            // point.mask_padding = Some(1.0);
            let nx = point.x / (cols - 1) as f64;
            let ny = point.y / (rows - 1) as f64;
            let value = heat_value(nx, ny);
            Some(format!(
                "cell: ({:.0}, {:.0})\nvalue: {:.3}",
                point.x, point.y, value
            ))
        })
        .with_cursor_overlay(true)
        .build()
        .unwrap()
}

fn heat_value(nx: f64, ny: f64) -> f64 {
    let gx = (nx - 0.35) / 0.18;