docs: def macd(series, fast=3, slow=10, smooth=16):
      """
      compute the MACD (Moving Average Convergence/Divergence)
      using a fast and slow exponential moving avg'
      return value is emaslow, emafast, macd which are len(x) arrays
      """
      macd_line = rolling_weighted_mean(series, window=fast) - \
          rolling_weighted_mean(series, window=slow)
      signal = rolling_weighted_mean(macd_line, window=smooth)
      histogram = macd_line - signal
      # return macd_line, signal, histogram
      return pd.DataFrame(index=series.index, data={
          'macd': macd_line.values,
          'signal': signal.values,
          'histogram': histogram.values
      })