Logarithmic axis

[ratwolf]

Is there an easy way to change the y-axis from linear to logarithmic?

use std::io;
use plotters::prelude::*;
use std::process::Command;

fn collatz(mut n: i128) -> Vec<i128> {
    let mut sequence = vec![n];

    while n != 1 {
        if n % 2 == 0 {
            n = n / 2;
        } else {
            n = 3 * n + 1;
        }
        sequence.push(n);
    }

    sequence
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    println!("Enter an integer for the Collatz sequence:");

    let mut input_value = String::new();
    io::stdin().read_line(&mut input_value)?;

    let input_value = match input_value.trim().parse::<i128>() {
        Ok(value) if value > 0 => value,
        _ => {
            println!("Invalid input. Please provide a valid positive integer.");
            return Ok(());
        }
    };

    let sequence = collatz(input_value);

    // Create a plot
    let root = BitMapBackend::new("collatz_sequence.png", (800, 600)).into_drawing_area();
    root.fill(&WHITE)?;

    let max_value = *sequence.iter().max().unwrap() as i128;

    let mut chart = ChartBuilder::on(&root)
        .caption("Collatz Sequence", ("sans-serif", 40))
        .x_label_area_size(50)
        .y_label_area_size(50)
        .build_cartesian_2d(0..sequence.len() as i128, 0..max_value)?;

    // Plot the Collatz sequence
    chart
        .configure_mesh()
        .x_labels(10)
        .y_labels(10)
        .draw()?;

    chart.draw_series(LineSeries::new(
        sequence.iter().enumerate().map(|(i, &val)| (i as i128, val)),
        &BLUE,
    ))?;

    // Finish the plot to ensure it's saved
    root.present()?;

    // Open the generated image using the 'open' command
    Command::new("open")
        .arg("collatz_sequence.png")
        .output()
        .expect("Failed to open image");

    Ok(())
}

[SkiFire13]

From a quick glance at the documentation it seems you need to import the plotters::coord::combinators::IntoLogRange and then change the line with buile_cartesian_2d into:

.build_cartesian_2d(0..sequence.len() as i128, (0..max_value).log_scale())?;

This should make the y axis log scale.

[ratwolf]

Thank you!

That worked ou fine. However I had to replace i128 with i64 in the code because i128 seems not to be supported.