/**
* Fractals Indicator (Bill Williams)
* 5-bar patterns that identify potential reversal points
*/
export interface FractalData {
bullishFractals: Array<{ index: number; value: number }>
bearishFractals: Array<{ index: number; value: number }>
currentBullishFractal: number | null
currentBearishFractal: number | null
signal: 'bullish_reversal' | 'bearish_reversal' | 'neutral' | null
}
export function calculateFractals(
highs: number[],
lows: number[],
currentPrice: number | null = null
): FractalData {
if (highs.length < 5 || lows.length < 5) {
return {
bullishFractals: [],
bearishFractals: [],
currentBullishFractal: null,
currentBearishFractal: null,
signal: null,
}
}
const bullishFractals: Array<{ index: number; value: number }> = []
const bearishFractals: Array<{ index: number; value: number }> = []
// Need at least 5 bars to check fractal pattern
// Check each bar from index 2 to length-3 (to have 2 bars before and after)
for (let i = 2; i < highs.length - 2; i++) {
// Bullish Fractal: High[2] > High[1] AND High[2] > High[3] AND High[2] > High[4] AND High[2] > High[5]
// (Note: array is 0-indexed, so High[2] is the center bar)
const isBullishFractal =
highs[i] > highs[i - 2] &&
highs[i] > highs[i - 1] &&
highs[i] > highs[i + 1] &&
highs[i] > highs[i + 2]
// Bearish Fractal: Low[2] < Low[1] AND Low[2] < Low[3] AND Low[2] < Low[4] AND Low[2] < Low[5]
const isBearishFractal =
lows[i] < lows[i - 2] &&
lows[i] < lows[i - 1] &&
lows[i] < lows[i + 1] &&
lows[i] < lows[i + 2]
if (isBullishFractal) {
bullishFractals.push({ index: i, value: highs[i] })
}
if (isBearishFractal) {
bearishFractals.push({ index: i, value: lows[i] })
}
}
// Get most recent fractals
const currentBullishFractal = bullishFractals.length > 0 ? bullishFractals[bullishFractals.length - 1].value : null
const currentBearishFractal = bearishFractals.length > 0 ? bearishFractals[bearishFractals.length - 1].value : null
// Determine signal based on current price position relative to recent fractals
let signal: 'bullish_reversal' | 'bearish_reversal' | 'neutral' | null = null
if (currentPrice && currentBullishFractal && currentBearishFractal) {
// If price breaks above recent bullish fractal, potential bullish continuation
if (currentPrice > currentBullishFractal) {
signal = 'bullish_reversal'
}
// If price breaks below recent bearish fractal, potential bearish continuation
else if (currentPrice < currentBearishFractal) {
signal = 'bearish_reversal'
} else {
signal = 'neutral'
}
}
return {
bullishFractals,
bearishFractals,
currentBullishFractal,
currentBearishFractal,
signal,
}
}
