Time aggregation: time_agg

Syntax

time_agg ( periodIndTo { , periodIndFrom } { , op } { , first | last } )

Input parameters

op	the scalar value, the Component or the Data Set to be converted. If not specified, then time_agg is used in combination within an aggregation operator
periodIndFrom	the source period indicator
periodIndTo	the target period indicator

Examples of valid syntaxes

sum ( DS group all time_agg ( “A” ) )
time_agg ( “A”, cast ( “2012Q1”, time_period , ”YYYY\Qq” ) )
time_agg(“M”, cast (“2012-12-23”, date, “YYYY-MM-DD”) )
time_agg(“M”, DS1)
ds_2 := ds_1[calc Me1 := time_agg(“M”,Me1)]

Semantics for scalar operations

The operator converts a time, date or time_period value from a smaller to a larger duration.

Input parameters type

op

dataset { identifier < time > _ , identifier _* }
| component<time>
| time

periodIndFrom, periodIndTo

duration

Result type

result

dataset { identifier < time > _ , identifier _* }
| component<time>
| time

Additional Constraints

If op is a Data Set then it has exactly one Identifier of type time, date or time_period and may have other Identifiers.

If time_agg is used in combination with an aggregation operator, op must not be specified, and the source dataset must have exactly one Identifier of type time, date or time_period (it may have additional Identifiers of other types).

It is only possible to convert smaller duration values to larger duration values (e.g. it is possible to convert monthly data to annual data but the contrary is not allowed).

Behaviour

The scalar version of this operator takes as input a time, date or time_period value, converts it to periodIndTo and returns a scalar of the corresponding type.

The Data Set version acts on a single Measure Data Set of type time, date or time_period and returns a Data Set having the same structure.

Finally, VTL also provides a component version, for use in combination with an aggregation operator, because the change of frequency requires an aggregation. In this case, the operator converts the period_indicator of the data points (e.g., convert monthly data to annual data).

On time type, the operator maps the input value into the comprising larger regular interval, whose duration is the one specified by the periodIndTo parameter.

On date type, the operator maps the input value into the comprising larger period, whose duration is the one specified by the periodIndTo parameter, which is conventionally represented either by the start or by the end date, according to the first/last parameter.

On time_period type, the operator maps the input value into the comprising larger time period specified by the periodIndTo parameter (the original period indicator is converted in the target one and the number of periods is adjusted correspondingly).

The input duration periodIndFrom is optional. In case of time_period Data Points, the input duration can be inferred from the internal representation of the value. In case of time or date types, it is inferred by the implementation.