/**
* Percentage Price Oscillator (PPO) Indicator
* MACD expressed as a percentage for easier comparison across different price levels
*/
import { calculateEMA } from './moving-averages'
export interface PPOData {
ppo: number | null
signal: number | null
histogram: number | null
signal_type: 'bullish' | 'bearish' | 'neutral' | null
}
export function calculatePPO(
closes: number[],
fastPeriod: number = 12,
slowPeriod: number = 26,
signalPeriod: number = 9
): PPOData {
if (closes.length < slowPeriod + signalPeriod) {
return {
ppo: null,
signal: null,
histogram: null,
signal_type: null,
}
}
// Calculate EMAs
const fastEMA = calculateEMA(closes, fastPeriod)
const slowEMA = calculateEMA(closes, slowPeriod)
if (fastEMA.length < slowPeriod - fastPeriod + 1 || slowEMA.length === 0) {
return {
ppo: null,
signal: null,
histogram: null,
signal_type: null,
}
}
// Align arrays and calculate PPO line: ((EMA_fast - EMA_slow) / EMA_slow) * 100
const ppoLine: number[] = []
const startIdx = slowPeriod - fastPeriod
for (let i = 0; i < slowEMA.length; i++) {
const fastValue = fastEMA[startIdx + i]
const slowValue = slowEMA[i]
if (fastValue && slowValue && slowValue !== 0) {
const ppo = ((fastValue - slowValue) / slowValue) * 100
ppoLine.push(ppo)
}
}
if (ppoLine.length === 0) {
return {
ppo: null,
signal: null,
histogram: null,
signal_type: null,
}
}
// Calculate PPO Signal (EMA of PPO line)
const ppoSignal = calculateEMA(ppoLine, signalPeriod)
if (ppoSignal.length === 0) {
return {
ppo: ppoLine[ppoLine.length - 1],
signal: null,
histogram: null,
signal_type: null,
}
}
// Get current values
const currentPPO = ppoLine[ppoLine.length - 1]
const currentSignal = ppoSignal[ppoSignal.length - 1]
const histogram = currentPPO - currentSignal
// Determine signal type
let signal_type: 'bullish' | 'bearish' | 'neutral' | null = null
if (histogram > 0) signal_type = 'bullish'
else if (histogram < 0) signal_type = 'bearish'
else signal_type = 'neutral'
return {
ppo: currentPPO,
signal: currentSignal,
histogram,
signal_type,
}
}
