{"id":12994,"date":"2018-04-10T11:45:40","date_gmt":"2018-04-10T06:15:40","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=12994"},"modified":"2021-05-09T13:16:01","modified_gmt":"2021-05-09T07:46:01","slug":"variables-in-sas","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/variables-in-sas\/","title":{"rendered":"FIRST. and LAST. Variables in SAS – How to Select the Variables"},"content":{"rendered":"

Previously, we have seen the SAS variable<\/a><\/strong>, today we will be looking at the use of FIRST. and LAST. variable in SAS Programming Language. We will discuss the working of\u00a0FIRST. and LAST. Variables in SAS and how to select SAS FIRST. Variable. At last, we will study how to select LAST. variables in SAS and calculate the cumulative score by the group.<\/p>\n

So, let’s start with the FIRST. and LAST. Variables in SAS.<\/p>\n

\"FIRST.<\/a><\/p>\n

What is FIRST. & LAST. Variables in SAS?<\/h2>\n

Anytime we wish to group our data in SAS Programming, we make use of the BY statement to tell the order of grouping and the SET statement to group data. Whenever both BY and SET statements are used together, SAS automatically creates two variables, FIRST. and LAST. Variables in SAS, that are temporary.<\/p>\n

SAS uses the value of the FIRST. and LAST. Variables to identify the first and last observations in a group. SAS<\/a> places FIRST. and LAST. Variable in SAS Program Data Vector (PDV).<\/strong> Then, they are available for DATA step processing but SAS does not add them to the output data set as\u00a0they are temporary in nature.<\/p>\n

Explore the concept – SAS Macro For Beginners<\/a><\/strong><\/p>\n

How FIRST. and LAST. Variables Works<\/h2>\n

When an observation is the first in a BY group, SAS sets the value of FIRST.variable<\/em>\u00a0to 1 for the variable whose value changed, as well as for all of the variables that follow in the BY statement. For all other observations in the BY group, the value of FIRST.variable<\/em>\u00a0is 0.<\/p>\n

Likewise, if the observation is the last in a BY group, SAS sets the value of LAST.variable\u00a0<\/em>to 1 for the variable whose value changes on the next observation, as well as for all the variables that follow in the BY statement. For all other observations in the BY group, the value of LAST.variable<\/em>\u00a0is 0. For the last observation in a data set, the value of all LAST.variable<\/em>\u00a0variables are set to 1.<\/p>\n

The values of both FIRST. and LAST. variables in SAS are either 1 or 0.<\/p>\n