plottersで正規分布を書く

正規分布と言うよりplottersのメモ。

cargo.toml

[package]  
name = "ch1_normal_distribution"  
version = "0.1.0"  
edition = "2021"  
  
[dependencies]  
plotters = "0.3.7"

ソースコード

  
use std::f64::consts::PI;  
use std::f64::consts::E;  
use plotters::prelude::*;  
  
fn normal(x:f64, mu:f64, sigma:f64) -> f64 {  
    let a = - (x - mu) * (x - mu) / (2.0 * sigma * sigma);  
    E.powf(a) / (sigma * (2.0 * PI).sqrt())  
  
}  
  
fn main() {  
    let mu = 0.0;  
    let sigma = 1.0;  
  
    let mut xs :Vec<f64> = vec![];  
    let mut ys :Vec<f64> = vec![];  
  
    let x_min = -5.0;  
    let x_max = 5.0;  
    let n = 100;  
  
    let step = (x_max - x_min) / n as f64;  
    for i in 0..n {  
        let x = x_min + step * i as f64;  
        let y = normal(x, mu, sigma);  
        xs.push(x);  
        ys.push(y);  
    }  
  
    let line = LineSeries::new(xs.iter().zip(ys.iter()).map(|(x, y )| (*x as f32, *y as f32)), &RED);  
  
    let root = BitMapBackend::new("plot.png", (640, 480)).into_drawing_area();  
    root.fill(&WHITE);  
  
    let mut chart = ChartBuilder::on(&root)  
        .caption("normal distribution", ("sans-serif", 35).into_font())  
        .margin(5)  
        .x_label_area_size(30)  
        .y_label_area_size(30)  
        .build_cartesian_2d(x_min as f32 ..x_max as f32, 0.0f32..1.0f32 ).unwrap();  
  
    chart.configure_mesh().draw();  
  
    chart  
        .draw_series(line).unwrap()  
        .label("y = normal(x, 0.0, 1.0)")  
        .legend(|(x, y)| PathElement::new(vec![(x, y), (x + 20, y)], &RED));  
  
    chart  
        .configure_series_labels()  
        .background_style(&WHITE.mix(0.8))  
        .border_style(&BLACK)  
        .draw().unwrap();  
  
    let _ = root.present();  
      
}

結果