Which variables are created when a sorted data set is read using the SET and BY statements?

When a sorted data set is read using the SET and BY statements in SAS, the system automatically generates two special variables: First. and Last. These variables are created to identify the first and last observations in each BY group.

The First. variable indicates the first observation of the current BY group, while the Last. variable signifies the last observation of the current BY group. These variables are particularly useful when performing operations or analyses that require group-specific calculations or when you need to summarize data by group.

For example, if you are analyzing sales data categorized by different regions, the First. variable would help you identify the first record for each region in your sorted data set, making it easier to perform calculations specific to each region.

The presence of these variables enhances the data manipulation capabilities within SAS, allowing programmers to effectively manage and analyze grouped data without requiring additional coding to track these boundaries.