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Keltner Channels

Classic volatility trend breakout channels classic

Uses the EMA-smoothed Atr, not Wilder's ATR

The Keltner channel width is built on QuantWave's Atr, which smooths true range with an EMA (alpha = 2/(period+1)) rather than Wilder's RMA (alpha = 1/period, SMA-seeded) used by TA-Lib and TradingView Pine's ta.atr. Upper/lower band distances differ from the Investopedia/Chester Keltner formulation and from most charting platforms.

No source has been recorded for the EMA smoothing — the formula_source recorded for this indicator describes the Wilder-based construction. See Average True Range for the full surface-by-surface breakdown, and quantwave.conventions("keltner") to read the divergence programmatically.

Keltner Channels are volatility-based envelopes set above and below an exponential moving average.

Visual Example

Keltner Channels — annotated preview mapping to core implementation

Synthetic ideal per library logic. Generated 2026-07-01 IST via docs/generate_all_previews.py (reproducible; maps to core Next<T> implementation).

Description

Keltner Channels are volatility-based envelopes set above and below an exponential moving average.

Use as volatility-adjusted envelope bands around an EMA. When Keltner Channels contract inside Bollinger Bands (the Squeeze), a high-energy breakout move is typically imminent.

Native Rust implementation with gold-standard or TA-Lib parity tests where applicable.

Keltner Channels, updated by Linda Raschke in the 1980s from Chester Keltner original design, use ATR to set channel width around an EMA. Unlike Bollinger Bands which use standard deviation, ATR-based channels adapt to average bar range rather than statistical volatility, producing smoother and more stable channel boundaries. — StockCharts ChartSchool

Typical applications:

  • Size stops and position risk from band width or ATR expansion
  • Detect squeeze conditions (narrow bands) before breakout systems
  • Warm-up: first 20 bars build rolling volatility state
  • Combine with trend direction (SuperTrend, MACD) for breakout bias

QuantWave implements this via the universal Next<T> trait — bit-identical across Rust streaming, Python streaming, and Polars .ta() batch plugins.

Formula / Specification

Implementation (quantwave-core/src/indicators/keltner.rs):

\[ UC = EMA + (Multiplier \times ATR) \]

Gold-standard parity vectors: quantwave-core/tests/gold_standard/keltner.json.

Parameters

Parameter Default Description
period 20 EMA Period
multiplier 2.0 ATR Multiplier

Usage Examples

Streaming (Rust)

use quantwave_core::indicators::KELTNER;
use quantwave_core::traits::Next;

let mut ind = KELTNER::new(20);
for price in &prices {
    let value = ind.next(price);
}

Streaming (Python)

from quantwave import KELTNER

ind = KELTNER(20)
for price in prices:
    value = ind.next(price)

Polars Batch (Python)

import polars as pl
import quantwave as qw

def apply_keltner_channels(series: pl.Series) -> pl.Series:
    ind = qw.KELTNER(20)
    return pl.Series([ind.next(float(v)) for v in series.to_list()])

df = (
    pl.read_csv('ohlcv.csv')
    .lazy()
    .with_columns(
        pl.col("close").map_batches(apply_keltner_channels, return_dtype=pl.Float64).alias("keltner_channels")
    )
    .collect()
)

All surfaces are bit-identical via the single Next<T> implementation and proptests.

Edge Cases & Limitations

  • Warm-up: first 20 bars may return NaN or partial state per implementation.
  • Parameter sensitivity: smaller periods increase noise; larger periods increase lag.
  • Sudden gaps or bad ticks can distort rolling windows — consider pre-filtering.
  • Single-series indicators ignore volume unless otherwise documented.
  • Validated via proptests against gold-standard vectors where available.
  • No look-ahead bias; streaming and Polars batch paths are bit-identical.

Boundary Behavior

Condition Behavior
Warm-up Leading bars return NaN until warmup_bars is satisfied.
period > len When period exceeds series length, output is all NaN.
NaN inputs NaN in input propagates to output (NaN out).
Invalid params Non-positive period or missing required params raise ValueError.
Empty data Empty input returns an empty result series.

Sources & References

Primary Source: https://www.investopedia.com/terms/k/keltnerchannel.asp

Implementation: quantwave-core/src/indicators/keltner.rs (KELTNER / KELTNER_METADATA). Parity: quantwave-core/tests/gold_standard/keltner.json

Provenance: Standards bulk upgrade 2026-07-01 IST — see docs/DOCUMENTATION_STANDARDS.md.