The @PERIOD variable is used in a calculation when you want to divide the amount in a row, column, or cell by a specified number of periods that will vary based upon the report or input date. Using @PERIOD allows for an easier method of calculating a monthly average, for example, without knowing at design time what month is in use on the report or input definition.
If periods are defined in the rows, @PERIOD in a column or row formula will be replaced by the effective period defined on the row being processed.
If periods are defined in the columns, then a given column formula will read the period value from the column on which it is set. A row formula using the @PERIOD replacement value in it will take the period from each column as it goes across.
@PERIOD also works with period ranges. If, for example the period is defined in a column and the column’s period is set to PERIOD-8, @PERIOD is replaced with the numeric value corresponding to 8 periods prior to the reporting period. If the column’s period is defined as “3 to 5”, the start of the range is used as the replacement for the @PERIOD variable, in this case 3.