What does the LAG function do in SAS?

The LAG function in SAS is designed to access values from previous observations in a dataset. When you use the LAG function, it retrieves the value of the specified variable from the previous row of data. This can be particularly useful in time series analysis or when evaluating changes from one observation to the next.

For example, if you're analyzing sales data and you want to compare the current month's sales to the previous month's sales, the LAG function enables you to pull the previous month's sales value into your calculations easily. The function maintains the integrity of your data while allowing you to perform sequential comparisons.

In contrast, the other options describe different types of operations that the LAG function does not perform. The calculation of differences between current and previous values involves a different function, while rounding numeric values and duplicating observations are unrelated tasks typically handled by other SAS functions or procedures.