Sas how does lag work

In this post, I will explain by example how the function works. Furthermore, I will demonstrate how to make the function produce the desired result. Even when handling By Groups. When programmers first encounter the Lag Function, they visualize a lookback. Which makes sense based on the name. However, this is a crucial mistake. Lag Function is not a lookback. Rather it is a queue. Let us think of it like this [. Both elements are missing at the start of execution.

Each time it executes, SAS returns the right-most value from the queue. Furthermore, the present value of the value we want to lag, is inserted into the queue from the left. The documentation describes a queue from bottom to top. However, I find it easier to present here with left to right. The principle is the same.

Let us look at an example. In the code below, I read the example data above. Connect and share knowledge within a single location that is structured and easy to search. I don't use sas so please take my answer as hint for usage of lag function, other issues such as date conversion or computing difference is up to you. This is solution in Postgres columns renamed to avoid clashes :. Dbfiddle here. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 1 year, 6 months ago. Active 1 year, 6 months ago. Viewed times. Improve this question. Usama Abdulrehman 1, 3 3 gold badges 9 9 silver badges 20 20 bronze badges. Khalid M Khalid M 3 2 2 bronze badges. Much easier in a Data Step. Thanks — Khalid M. This is best done in a data step, unless your data is in a database and your are using a remote connection.

I will now look into automating the results to a local ftp from SAS everyday. Thanks : — Khalid M. The only difference is we need to incorporate grouping variable to calculate lead by a grouping variable ID. N; quit;. It can also calculate moving averages. Spread the Word!

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