Quickstart

Stream a first indicator

This is examples/basic_indicator.rs from the repository:

use kestrel_chartkit::{build_checked, Bar, Indicator};
use std::collections::HashMap;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut params = HashMap::new();
    params.insert("rsi_len".to_string(), 14.0);
    let mut rsi = build_checked("rsi", &params)?;

    let closes = [
        44.34, 44.09, 44.15, 43.61, 44.33, 44.83, 45.10, 45.42, 45.84, 46.08, 45.89, 46.03, 45.61,
        46.28, 46.28, 46.00,
    ];

    for (i, &close) in closes.iter().enumerate() {
        let bar = Bar::try_new(
            1_700_000_000 + i as i64 * 60,
            close,
            close + 0.5,
            close - 0.5,
            close,
            1_000.0,
        )?;

        match rsi.on_bar(&bar) {
            Some(output) => println!("bar {i:>2}: close={close:.2}  RSI(14)={:.2}", output.value),
            None => println!("bar {i:>2}: close={close:.2}  RSI(14)=<warming up>"),
        }
    }

    Ok(())
}

cargo run --example basic_indicator prints:

bar  0: close=44.34  RSI(14)=<warming up>
bar  1: close=44.09  RSI(14)=<warming up>
…
bar 13: close=46.28  RSI(14)=<warming up>
bar 14: close=46.28  RSI(14)=70.46
bar 15: close=46.00  RSI(14)=68.36

Three things to note:

• build_checked validates the parameters against the registry and returns a boxed Indicator. An unknown name, an unknown parameter key or an out-of-range period is a RegistryError, not a panic.
• Bar::try_new rejects non-finite or non-positive prices and a high/low range that does not contain open and close. Use it wherever bars enter your program.
• on_bar returns None until the warmup is complete, then Some on every bar. The first value arrives on bar warmup_period().

Draw it

kestrel-chartkit computes and draws nothing. Hand the values to a renderer — chartlet for a static chart, as on this site, or kestrel-loom for an interactive one in the browser. The visualising guide shows how the site turns indicator output into a chartlet specification.

Next steps

• Indicators: the trait, the registry and the output fields.
• Market regime and Composite scoring.
• Visualising results: chartlet, kestrel-loom and the quick-look renderers.