PopExtPeriod
Using extended periods
Some calculations need an extended period to produce correct and consistent results. For example, calculating a delta series needs the previous value; calculating accumulated series from the start of the year needs all values from this point, even if the requested period is September that year. In Mesh calculations, the functions that inherently need extended periods, are handled implicitly when creating the calculation expressions.
Still, there may be situations where you explicitly want to define extended periods. To do this you can use the PushExtPeriod and PopExtPeriod functions to ensure correct behavior.
The ground rules for applying the Push/Pop mechanism are:
- The expression uses data outside the requested period to produce correct results.
- The time series that need to be extended has no direct database connection, i.e. it cannot be extended by reading more data from the database.
About the function
This function removes the extended calculation period created by PushExtPeriod. The function must always be used after PushExtPeriod.
Syntax
- PopExtPeriod(s)
Description
| Type | Description |
|---|---|
| s | Logic name of the period. It is the same as used in the corresponding PushExtPeriod. |
Note! The first argument name can be associated with a positional column time series name in a Time series report. Such names are 'A', 'B', 'C' --> 'AA', 'AB' etc. Thus, we recommend using a lower case letter in the first argument to PushExtPeriod and corresponding PopExtPeriod.
Example
The following two examples illustrate a period extension using both the Push and Pop functions. In both cases, this is handled implicitly in Mesh by the DELTA and PERCENTILE functions:
@PushExtPeriod( ‘X’, ‘-1h’, ‘0h’)
Tmp1 = 10 * @t( ‘TimeSeries’ )
@PopExtPeriod(‘X’)
## = @DELTA(Tmp1)
Uses relative period extension to get an extra hour at start so that DELTA gets what it needs to calculate the first value in the requested period.
@PushExtPeriod('P','20000101000000000','20100101000000000')
Corrected = @CorrectInterpolate(@ValidateAbsLimit( @RESET_STATUS
(@t('Temperature')),-25,25), 10, 'TRUE')
@PopExtPeriod('P')
## = @PERCENTILE(Corrected, 2000,2010,75)
Uses fixed period extension in line with the arguments to the PERCENTILE function on the last line.