function calculateDMI(prices, periods) {
  let pdi = [];
  let ndi = [];
  let atr = [];
  let dmi = [];

  for (let i = 0; i < prices.length; i++) {
    // Calculate the positive directional index (PDI)
    let upMove = prices[i].high - prices[i - 1].high;
    let downMove = prices[i - 1].low - prices[i].low;
    let pdiValue = 0;
    if (upMove > downMove && upMove > 0) {
      pdiValue = upMove;
    }
    pdi.push(pdiValue);

    // Calculate the negative directional index (NDI)
    let ndiValue = 0;
    if (downMove > upMove && downMove > 0) {
      ndiValue = downMove;
    }
    ndi.push(ndiValue);

    // Calculate the average true range (ATR)
    let tr = Math.max(
      prices[i].high - prices[i].low,
      Math.abs(prices[i].high - prices[i - 1].close),
      Math.abs(prices[i].low - prices[i - 1].close)
    );
    let atrValue = 0;
    if (i < periods) {
      atrValue = tr;
    } else {
      atrValue = (atr[i - 1] * (periods - 1) + tr) / periods;
    }
    atr.push(atrValue);

    // Calculate the directional movement index (DMI)
    let dmiValue = 0;
    if (atrValue > 0) {
      dmiValue = (pdi[i] / atrValue) - (ndi[i] / atrValue);
    }
    dmi.push(dmiValue);
  }

  return { pdi, ndi, atr, dmi };
}