/**
* Alligator Indicator (Bill Williams)
* Three smoothed moving averages representing different phases of market
*/
// Local SMMA helper function that calculates SMMA at a specific offset from the end
function calcSMMAAtOffset(values, period, offset) {
// We need at least (period + offset) data points
if (values.length < period + offset) {
return null;
}
// Calculate SMMA up to (length - offset) index
const endIndex = values.length - offset;
const slicedValues = values.slice(0, endIndex);
if (slicedValues.length < period) {
return null;
}
// Start with SMA for the first period
let smma = slicedValues.slice(0, period).reduce((sum, val) => sum + val, 0) / period;
// Continue with SMMA calculation
for (let i = period; i < slicedValues.length; i++) {
smma = (smma * (period - 1) + slicedValues[i]) / period;
}
return smma;
}
export function calculateAlligator(closes, jawPeriod = 13, teethPeriod = 8, lipsPeriod = 5, jawShift = 8, teethShift = 5, lipsShift = 3) {
// Minimum 5 data points required
if (closes.length < 5) {
return {
jaw: null,
teeth: null,
lips: null,
phase: null,
trend: null,
};
}
// Use adaptive periods based on available data
const dataRatio = Math.min(1, closes.length / (jawPeriod + jawShift));
const effectiveJawPeriod = Math.max(3, Math.floor(jawPeriod * dataRatio));
const effectiveTeethPeriod = Math.max(2, Math.floor(teethPeriod * dataRatio));
const effectiveLipsPeriod = Math.max(2, Math.floor(lipsPeriod * dataRatio));
const effectiveJawShift = Math.max(1, Math.floor(jawShift * dataRatio));
const effectiveTeethShift = Math.max(1, Math.floor(teethShift * dataRatio));
const effectiveLipsShift = Math.max(1, Math.floor(lipsShift * dataRatio));
// Calculate SMMA for each line with their respective offsets (shifts)
let jaw = calcSMMAAtOffset(closes, effectiveJawPeriod, effectiveJawShift);
let teeth = calcSMMAAtOffset(closes, effectiveTeethPeriod, effectiveTeethShift);
let lips = calcSMMAAtOffset(closes, effectiveLipsPeriod, effectiveLipsShift);
// Fallback: if any is null, use simple moving average
if (jaw === null || teeth === null || lips === null) {
const avgPrice = closes.slice(-Math.min(5, closes.length)).reduce((a, b) => a + b, 0) / Math.min(5, closes.length);
if (jaw === null)
jaw = avgPrice * 0.98;
if (teeth === null)
teeth = avgPrice * 0.99;
if (lips === null)
lips = avgPrice;
}
// Determine market phase based on Alligator lines
let phase = null;
let trend = null;
// Check if lines are intertwined (sleeping phase)
const avgVal = (jaw + teeth + lips) / 3;
const threshold = avgVal * 0.001; // 0.1% threshold
const linesClose = Math.abs(jaw - teeth) < threshold && Math.abs(teeth - lips) < threshold && Math.abs(jaw - lips) < threshold;
if (linesClose) {
phase = 'sleeping';
trend = 'neutral';
}
else {
// Check order of lines
if (lips > teeth && teeth > jaw) {
phase = 'eating';
trend = 'bullish';
}
else if (jaw > teeth && teeth > lips) {
phase = 'satiated';
trend = 'bearish';
}
else {
phase = 'waking';
trend = 'neutral';
}
}
return {
jaw,
teeth,
lips,
phase,
trend,
};
}
