Example 8.13 Obtaining the Previous Value of a Variable within a BY Group
Create variables that have the values of a variable from previous observations. Process the data set in BY groups so that the process of obtaining lagged values starts over with each new BY group.
This example uses the same input data set as Example 8.14.
|Featured Step||DATA step|
|Featured Step Options and Statements||LAGn function|
|Related Technique||DATA step, BY and RETAIN statements, FIRST. and LAST. automatic variables|
|A Closer Look||More on the DATA Step in This Example|
Input Data Set
Data set PRODUCTION records the number of units of an item made on several days at four plant locations.
PRODUCTION units_ Obs plant proddate made 1 Aux Plant 03/02/2009 ...