nRange
a lookback window for the range
  computation. A number above 7 results in the following
  computation: take the difference between the nRange max
  high and min low. Add up that value, that value lagged by
  nRange+1, nRange*2, nRange*3, and nRange*4, and divide by
  25. If nRange is 7 or less, the daily range is instead
  computed as the 5-day SMA of the following quantity: for
  each day, take the maximum of the difference between the
  high and low, or the absolute difference between current
  and previous close. Multiply that final quantity by .16.