RustQuant 0.0.4

use plotters::prelude::*;
use std::error::Error;
use std::fs::File;
use std::io::Write;

/// Write vector to file.
pub fn write_vector(v: &[f64]) -> Result<(), Box<dyn Error>> {
    let strings: Vec<String> = v.iter().map(|n| n.to_string()).collect();

    let mut file = File::create("vector.out")?;
    writeln!(file, "{}", strings.join(", "))?;
    Ok(())
}

/// Prepare vector for plotting in `plot_vector()`.
fn prepare_vec(vals: Vec<f64>) -> (Vec<(f64, f64)>, f64, f64) {
    let mut out = vec![(0.0, 0.0); vals.len()];
    let mut min = vals[0];
    let mut max = vals[0];

    for i in 0..vals.len() {
        out[i] = (i as f64, vals[i]);
        if vals[i] > max {
            max = vals[i]
        } else if vals[i] < min {
            min = vals[i]
        }
    }
    (out, min, max)
}

/// Plot a vector of values.
pub fn plot_vector(v: Vec<f64>, file: &str) -> Result<(), Box<dyn std::error::Error>> {
    let (vec2d, min, max) = prepare_vec(v);

    let root = BitMapBackend::new(file, (640, 480)).into_drawing_area();

    root.fill(&WHITE)?;

    let mut chart = ChartBuilder::on(&root)
        .caption(file, ("sans-serif", 30).into_font())
        .margin(5)
        .x_label_area_size(30)
        .y_label_area_size(30)
        .build_cartesian_2d(0f64..vec2d.len() as f64, min..max)?;

    chart.configure_mesh().draw()?;

    chart.draw_series(LineSeries::new(vec2d, RED))?.label(file);

    chart
        .configure_series_labels()
        .background_style(WHITE.mix(0.8))
        .border_style(BLACK)
        .draw()?;

    Ok(())
}