Calculate Parabolic SAR (Stop And Reverse) In JavaScript?

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To calculate the Parabolic SAR (Stop and Reverse) in JavaScript, you can use the formula provided by Welles Wilder Jr. The Parabolic SAR is a technical indicator used to determine potential reversals in the price movement of an asset. It is based on the idea that a trailing stop-and-reverse trading signal is generated when the price intersects the SAR line.


To calculate the Parabolic SAR, you first need to determine the initial SAR value. Once you have the initial value, you can then calculate the SAR value for each subsequent period. The formula involves taking the previous SAR value, adjusting it based on the acceleration factor, and then comparing it against the extreme point (highest high or lowest low) of the current period.


By implementing this calculation in JavaScript, you can create a function that takes in the necessary input values (such as the high and low prices of the asset) and returns the corresponding Parabolic SAR value for each period. This can be useful for traders and analysts looking to incorporate the Parabolic SAR indicator into their technical analysis toolkit.

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How to calculate the next SAR value based on current values in JavaScript?

To calculate the next SAR (Stop and Reverse) value based on current values, you can use the following formula:


SARn+1 = SARn + AF * (EP - SARn)


Where:

  • SARn+1 is the next SAR value
  • SARn is the current SAR value
  • AF is the acceleration factor
  • EP is the highest high for a long position or the lowest low for a short position


Here's a JavaScript function that implements this calculation:

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function calculateSAR(currentSAR, accelerationFactor, extremePoint, isLongPosition) {
  // Calculate the SAR for the next period
  let nextSAR = currentSAR + accelerationFactor * (extremePoint - currentSAR);
  
  // Adjust acceleration factor if necessary
  if (isLongPosition) {
    if (currentSAR < extremePoint) {
      accelerationFactor += 0.02;
    } else {
      accelerationFactor = 0.02;
    }
  } else {
    if (currentSAR > extremePoint) {
      accelerationFactor += 0.02;
    } else {
      accelerationFactor = 0.02;
    }
  }
  
  // Return the calculated next SAR value and the updated acceleration factor
  return { nextSAR, accelerationFactor };
}

// Example usage
let currentSAR = 10;
let accelerationFactor = 0.02;
let extremePoint = 12;
let isLongPosition = true;

let result = calculateSAR(currentSAR, accelerationFactor, extremePoint, isLongPosition);
console.log("Next SAR value: " + result.nextSAR);
console.log("Updated acceleration factor: " + result.accelerationFactor);


In this function, you can provide the current SAR value, acceleration factor, extreme point, and whether it is a long or short position. The function then calculates the next SAR value and updates the acceleration factor accordingly.


How to calculate Parabolic SAR for different timeframes in JavaScript?

Here is a sample JavaScript code to calculate Parabolic SAR for different timeframes:

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// Function to calculate Parabolic SAR for a given timeframe
function calculateParabolicSAR(timeframe, data) {
  let acceleration = 0.02;
  let accelerationMax = 0.20;
  let SAR = [];
  
  for (let i = 0; i < data.length; i++) {
    if (i < timeframe) {
      SAR.push(null);
      continue;
    }
    
    let high = Math.max(...data.slice(i - timeframe, i).map(d => d.high));
    let low = Math.min(...data.slice(i - timeframe, i).map(d => d.low));
    
    let previousSAR = i === timeframe ? data[i - 1].close : SAR[i - 1];
    
    let EP = data[i].high > high ? high : data[i].low < low ? low : previousSAR;
    
    if (previousSAR < data[i - 1].low) {
      acceleration = Math.min(acceleration + 0.02, accelerationMax);
    } else if (previousSAR > data[i - 1].high) {
      acceleration = 0.02;
    }
    
    let newSAR = previousSAR + acceleration * (EP - previousSAR);
    
    SAR.push(newSAR);
  }
  
  return SAR;
}

// Sample data
let data = [
  { high: 10, low: 5, close: 8 },
  { high: 12, low: 7, close: 9 },
  { high: 15, low: 8, close: 11 },
  // Add more data points here
];

// Calculate Parabolic SAR for a 3-day timeframe
let parabolicSAR_3day = calculateParabolicSAR(3, data);
console.log(parabolicSAR_3day);

// Calculate Parabolic SAR for a 5-day timeframe
let parabolicSAR_5day = calculateParabolicSAR(5, data);
console.log(parabolicSAR_5day);


In this code snippet, we have defined a calculateParabolicSAR function that takes a timeframe and an array of data objects as input and returns an array of Parabolic SAR values for the given timeframe. The function calculates the SAR values based on the High, Low, and Close prices of the data points and updates the SAR value according to the acceleration factor.


You can call this function with different timeframes to calculate Parabolic SAR values for different periods.


How to validate Parabolic SAR signals with price action analysis?

To validate Parabolic SAR signals with price action analysis, follow these steps:

  1. Confirm the direction of the Parabolic SAR indicator: Check if the Parabolic SAR dots are above the price action, indicating a downtrend, or below the price action, indicating an uptrend.
  2. Look for key support and resistance levels: Identify areas where price has previously reversed or found support/resistance. If the Parabolic SAR signal aligns with these levels, it adds validity to the signal.
  3. Analyze candlestick patterns: Look for bullish or bearish candlestick patterns that confirm the direction of the Parabolic SAR signal. For example, a bullish engulfing pattern can validate a buy signal, while a bearish engulfing pattern can validate a sell signal.
  4. Watch for price action confirming signals: Look for price action confirming signals such as trendline breaks, moving average crossovers, or chart patterns (e.g. head and shoulders, double tops/bottoms) that support the Parabolic SAR signal.
  5. Consider volume: Pay attention to the volume accompanying the price movements. Higher volume can validate the strength of the signal, while low volume may indicate a lack of conviction in the market.


By combining Parabolic SAR signals with price action analysis, you can increase the reliability of your trading decisions and have a more comprehensive understanding of market dynamics.

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