/**
* Keltner Channels Indicator
* Volatility-based channels using ATR around EMA
*/
import { calculateEMA } from './moving-averages';
import { calculateATR } from './volatility';
export function calculateKeltnerChannels(highs, lows, closes, emaPeriod = 20, atrPeriod = 14, multiplier = 2) {
// Minimum 5 data points required
if (closes.length < 5) {
return {
middle: null,
upper: null,
lower: null,
bandwidth: null,
position: null,
trend: null,
};
}
// Use adaptive periods
const effectiveEmaPeriod = Math.min(emaPeriod, closes.length);
const effectiveAtrPeriod = Math.min(atrPeriod, closes.length - 1);
// Calculate EMA for middle line
const ema = calculateEMA(closes, effectiveEmaPeriod);
let currentEMA = ema[ema.length - 1];
if (!currentEMA) {
// Fallback: use simple average
currentEMA = closes.slice(-effectiveEmaPeriod).reduce((a, b) => a + b, 0) / effectiveEmaPeriod;
}
// Calculate ATR
const atr = calculateATR(highs, lows, closes, effectiveAtrPeriod);
let currentATR = atr[atr.length - 1];
if (!currentATR) {
// Fallback: calculate simple ATR
let trSum = 0;
for (let i = 1; i < Math.min(effectiveAtrPeriod + 1, closes.length); i++) {
const tr = Math.max(highs[i] - lows[i], Math.abs(highs[i] - closes[i - 1]), Math.abs(lows[i] - closes[i - 1]));
trSum += tr;
}
currentATR = trSum / Math.max(1, Math.min(effectiveAtrPeriod, closes.length - 1));
}
// Calculate channels
const upper = currentEMA + (multiplier * currentATR);
const lower = currentEMA - (multiplier * currentATR);
const bandwidth = (upper - lower) / currentEMA;
// Determine trend (expanding/contracting based on ATR change)
let trend = null;
if (atr.length >= 2) {
const currentATR = atr[atr.length - 1];
const previousATR = atr[atr.length - 2];
const atrChange = (currentATR - previousATR) / previousATR;
if (atrChange > 0.05)
trend = 'expanding'; // ATR increased > 5%
else if (atrChange < -0.05)
trend = 'contracting'; // ATR decreased > 5%
else
trend = 'stable';
}
return {
middle: currentEMA,
upper,
lower,
bandwidth,
position: null, // Will be set by caller with current price
trend,
};
}
