ID variable INTERVAL= interval options ;

The ID statement names a numeric variable that identifies observations in the input and output data sets. The ID variable’s values are assumed to be SAS date, time, or datetime values. In addition, the ID statement specifies the (desired) frequency associated with the time series. The ID statement options also specify how the observations are accumulated and how the time ID values are aligned to form the time series. The options specified affect all variables listed in subsequent INPUT and TARGET statements. If an ID statement is specified, the INTERVAL= option must also be specified. The other ID statement options are optional. If an ID statement is not specified, the observation number, with respect to the BY group, is used as the time ID.

The following options can be used with the ID statement.

ACCUMULATE=option

specifies how the data set observations are accumulated within each time period. The frequency (width of each time interval) is specified by the INTERVAL= option. The ID variable contains the time ID values. Each time ID variable value corresponds to a specific time period. The accumulated values form the time series, which is used in subsequent analysis.

The ACCUMULATE= option is particularly useful when there are zero or more than one input observations coinciding with a particular time period (for example, time-stamped transactional data). The EXPAND procedure offers additional frequency conversions and transformations that can also be useful in creating a time series.

The following options determine how the observations are accumulated within each time period based on the ID variable and the frequency specified by the INTERVAL= option:

NONE

No accumulation occurs; the ID variable values must be equally spaced with respect to the frequency. This is the default option.

TOTAL

Observations are accumulated based on the total sum of their values.

AVERAGE | AVG

Observations are accumulated based on the average of their values.

MINIMUM | MIN

Observations are accumulated based on the minimum of their values.

MEDIAN | MED

Observations are accumulated based on the median of their values.

MAXIMUM | MAX

Observations are accumulated based on the maximum of their values.

N

Observations are accumulated based on the number of nonmissing observations.

NMISS

Observations are accumulated based on the number of missing observations.

NOBS

Observations are accumulated based on the number of observations.

FIRST

Observations are accumulated based on the first of their values.

LAST

Observations are accumulated based on the last of their values.

STDDEV |STD

Observations are accumulated based on the standard deviation of their values.

CSS

Observations are accumulated based on the corrected sum of squares of their values.

USS

Observations are accumulated based on the uncorrected sum of squares of their values.

If the ACCUMULATE= option is specified, the SETMISSING= option is useful for specifying how accumulated missing values are treated. If missing values should be interpreted as zero, then SETMISSING=0 should be used. The DETAILS section describes accumulation in greater detail.

ALIGN=option

controls the alignment of SAS dates that are used to identify output observations. The ALIGN= option accepts the following values: BEGINNING|BEG|B, MIDDLE|MID|M, and ENDING|END|E. ALIGN=BEGINNING is the default.

END=option

specifies a SAS date, datetime, or time value that represents the end of the data. If the last time ID variable value is less than the END= value, the series is extended with missing values. If the last time ID variable value is greater than the END= value, the series is truncated. For example, END="&sysdate"D uses the automatic macro variable SYSDATE to extend or truncate the series to the current date. The START= and END= options can be used to ensure that data associated within each BY group contains the same number of observations.

FORMAT=format

specifies the SAS format for the time ID values. If the FORMAT= option is not specified, the default format is implied by the INTERVAL= option. For example, FORMAT=DATE9. specifies that the DATE9. SAS format is to be used. Notice that the terminating "." is required when specifying a SAS format.

INTERVAL= interval

specifies the frequency of the accumulated time series. For example, if the input data set consists of quarterly observations, then INTERVAL=QTR should be used. If the SEASONALITY= option is not specified, the length of the seasonal cycle is implied from the INTERVAL= option. For example, INTERVAL=QTR implies a seasonal cycle of length 4. If the ACCUMULATE= option is also specified, the INTERVAL= option determines the time periods for the accumulation of observations.

NOTSORTED

specifies that the time ID values are not in sorted order. The SIMILARITY procedure sorts the data with respect to the time ID prior to analysis if the NOTSORTED option is specified.

SETMISSING=option | number

specifies how missing values (either actual or accumulated) are interpreted in the accumulated time series. If a number is specified, missing values are set to that number. If a missing value indicates an unknown value, the SETMISSING= option should not be used. If a missing value indicates no value, then SETMISSING=0 should be used. You typically use SETMISSING=0 for transactional data, because no recorded data usually implies no activity. The following options can also be used to determine how missing values are assigned:

MISSING

Missing values are set to missing. This is the default option.

AVERAGE | AVG

Missing values are set to the accumulated average value.

MINIMUM | MIN

Missing values are set to the accumulated minimum value.

MEDIAN | MED

Missing values are set to the accumulated median value.

MAXIMUM | MAX

Missing values are set to the accumulated maximum value.

FIRST

Missing values are set to the accumulated first nonmissing value.

LAST

Missing values are set to the accumulated last nonmissing value.

PREVIOUS | PREV

Missing values are set to the previous period’s accumulated nonmissing value. Missing values at the beginning of the accumulated series remain missing.

NEXT

Missing values are set to the next period’s accumulated nonmissing value. Missing values at the end of the accumulated series remain missing.

START= option

specifies a SAS date, datetime, or time value that represents the beginning of the data. If the first time ID variable value is greater than the START= value, the series is prepended with missing values. If the first time ID variable value is less than the START= value, the series is truncated. The START= and END= options can be used to ensure that data associated with each BY group contains the same number of observations.

ZEROMISS=option

specifies how beginning and/or ending zero values (either actual or accumulated) are interpreted in the accumulated time series. The following options can also be used to determine how beginning and/or ending zero values are assigned:

NONE

Beginning and/or ending zeros are unchanged. This is the default.

LEFT

Beginning zeros are set to missing.

RIGHT

Ending zeros are set to missing.

BOTH

Both beginning and ending zeros are set to missing.

If the accumulated series is all missing and/or zero, the series is not changed.