Some formulas require you to define a window length.

Let’s take as example the formula for a rolling mean:

Mean(series, window)

For the window length you should input the* number of observations* over which the function will be calculated. The number of observations is based on the frequency of the document.

Instead of typing a number, you may also use other formulas to get the number of observations in a specified period, such as *YearsLength(1)*, *QuartersLength(4)* or *MonthsLength(12)*.

For example, you can calculate the one year rolling mean of a series, by using the following formula:

Mean(series, YearsLength(1))

The advantage of this is that it is not necessary to concentrate on the frequency of the document in order to determine the number of observations.

For more information: