LETTERS TO S&C
LOOKBACK OR LENGTH?
I have a question that deals with the formula listed on page 30 of the February 1991 issue. When
calculating the formula gives a lookback length of one through 20 days, is the average range based on the
current lookback length or is it the length of the total data series up to the day of the calculation? For
data of 100 days, currently at 40
start with lookback of 2. avg.rng = 2,
avg (h- 1, past two days)
start with lookback of 3. avg.rng = 3,
avg (b - 1, past three days).
avg.rng = avg (h-1, day 1 to 40)?
The average range is based on the current lookback length.