The SIMILARITY Procedure

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 that coincide 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:

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 section Details: SIMILARITY Procedure describes accumulation in greater detail.

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.

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 that are associated within each BY group contain the same number of observations.

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 be used. Notice that the terminating “.” is required when specifying a SAS format.

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.

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.

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:

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 that are associated with each BY group contain the same number of observations.

specifies how beginning and 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 ending zero values are assigned:

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