charton 0.4.1

A high-level, layered charting system for Rust, designed for Polars-first data workflows and multi-backend rendering.
Documentation 
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use charton::prelude::*;
use polars::prelude::*;
use std::error::Error;

#[test]
fn test_errorbar_1() -> Result<(), Box<dyn Error>> {
    // Create sample data with multiple points having the same x values,
    // which allows calculating mean and standard deviation
    let df = df! [
        "x" => ["a", "a", "a", "b", "b", "b", "c", "c", "c", "d", "d", "d"],
        "y" => [5.1, 5.3, 5.7, 6.5, 6.9, 6.2, 4.0, 4.2, 4.4, 7.6, 8.0, 7.8],
    ]?;

    // Create error bar chart
    Chart::build(&df)?
        .mark_errorbar()?
        .configure_errorbar(|e| {
            e.with_color("blue")
                .with_stroke_width(2.0)
                .with_cap_length(5.0)
                .with_center(true)
        })
        .encode((x("x"), y("y")))?
        .with_size(500, 400)
        .with_title("Error Bar Chart with Mean and Std Dev")
        .save("./tests/errorbar_1.svg")?;

    Ok(())
}

#[test]
fn test_errorbar_2() -> Result<(), Box<dyn Error>> {
    // 1. Create sample data with an extra "group" column
    // Each combination of (x, group) has multiple values for std dev calculation
    let df = df! [
        "x"     => ["A", "A", "A", "A", "A", "A", "B", "B", "B", "B", "B", "B"],
        "y"     => [10.0, 12.0, 11.0, 15.0, 17.0, 16.0, 8.0, 9.0, 8.5, 12.0, 14.0, 13.0],
        "group" => ["G1", "G1", "G1", "G2", "G2", "G2", "G1", "G1", "G1", "G2", "G2", "G2"],
    ]?;

    // 2. Build the Error Bar layer
    let errorbar_layer = Chart::build(&df)?
        .mark_errorbar()?
        // Mapping 'group' to color triggers the dodge logic
        .encode((x("x"), y("y"), color("group")))?;

    // 3. (Optional but recommended) Add a Bar layer to see the alignment
    let bar_layer = Chart::build(&df)?.mark_bar()?.encode((
        x("x"),
        y("y").with_aggregate("mean"),
        color("group"),
    ))?;

    // 4. Create the Layered Chart
    errorbar_layer
        .and(bar_layer)
        .with_size(600, 400)
        .with_title("Grouped Error Bars with Mean & Std Dev")
        .save("./tests/errorbar_2.svg")?;

    Ok(())
}