RSI with EMA

function calculateRSIAndEMA() {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("test");
  var range = sheet.getRange("B2:B");
  var data = range.getValues();

  // Read lengths from cells G2 and G4
  var rsiPeriod = sheet.getRange("G2").getValue();
  var emaPeriod = sheet.getRange("G4").getValue();

  var closingPrices = [];
  for (var i = 0; i < data.length; i++) {
    if (data[i][0] == '') break; // Stop if an empty cell is encountered
    closingPrices.push(data[i][0]);
  }

  var rsi = calculateRSIArray(closingPrices, rsiPeriod);
  var ema = calculateEMA(rsi, emaPeriod);

  // Write RSI to column C and EMA of RSI to column D
  for (var j = 0; j < closingPrices.length; j++) {
    if (j < rsiPeriod) {
      sheet.getRange(j + 2, 3).setValue("-");
      sheet.getRange(j + 2, 4).setValue("-");
    } else {
      sheet.getRange(j + 2, 3).setValue(rsi[j - rsiPeriod]);
      if (j < rsiPeriod + emaPeriod - 1) {
        sheet.getRange(j + 2, 4).setValue("-");
      } else {
        sheet.getRange(j + 2, 4).setValue(ema[j - rsiPeriod - (emaPeriod - 1)]);
      }
    }
  }
}

function calculateRSIArray(closingPrices, period) {
  var rsiArray = [];
  var gain = 0;
  var loss = 0;

  for (var i = 1; i <= period; i++) {
    var change = closingPrices[i] - closingPrices[i - 1];
    if (change > 0) {
      gain += change;
    } else {
      loss -= change;
    }
  }

  gain = gain / period;
  loss = loss / period;

  if (loss == 0) {
    rsiArray.push(100);
  } else {
    var rs = gain / loss;
    rsiArray.push(100 - (100 / (1 + rs)));
  }

  for (var j = period; j < closingPrices.length; j++) {
    var change = closingPrices[j] - closingPrices[j - 1];
    if (change > 0) {
      gain = (gain * (period - 1) + change) / period;
      loss = (loss * (period - 1)) / period;
    } else {
      gain = (gain * (period - 1)) / period;
      loss = (loss * (period - 1) - change) / period;
    }

    if (loss == 0) {
      rsiArray.push(100);
    } else {
      rs = gain / loss;
      rsiArray.push(100 - (100 / (1 + rs)));
    }
  }

  return rsiArray;
}

function calculateEMA(data, period) {
  var emaArray = [];
  var k = 2 / (period + 1);

  // Start EMA with the first available RSI value
  var ema = data[0];
  emaArray.push(ema);

  for (var i = 1; i < data.length; i++) {
    ema = data[i] * k + ema * (1 - k);
    emaArray.push(ema);
  }

  return emaArray;
}