SAS How To's

How to Add Row Numbers in SAS

Row Numbers

Sometimes you need a column in your data set that indicates the row number. This might be useful as an artificial identifier, a rank, or something else. In this article, we explain two ways how to add row numbers in SAS.

Adding Row Numbers with _N_ in a Data Step

The first option to create a column with row numbers is using the automatic _N_ variable. SAS processes input data row by row and the automatic _N_variable stores the current row number. This variable is particularly useful for processing the first or last row. However, since _N_ is a variable you can also use it to add a column with row numbers.

Adding Row Number with monotonic() in PROC SQL

The automatic _N_ variable can only be used in data steps. However, you can use the monotonic() function in PROC SQL. The monotonic function is undocumented and generates sequential numbers.

Example: Adding Row Numbers

In the following example code, we demonstrate how to apply both options of how to add row numbers. First, we create a data set and then we add the row numbers. The three images at the end show the original data set and the two data set with the new column.

/* CREATE A DATA SET */
data work.examscores;
	input name $ score;
	datalines;
Jim 80
Maria 85
Bob 50
Cris 70
John 95
Kate 95
George 80
Susan 75
Joe 55
Jennifer 75
Lu 60
Antonio 85
;
run;

/* ADD ROW NUMBER (I) */
data work.examscores_I;
	set work.examscores;
	
	rownumber_I = _N_;
run;


/* ADD ROW NUMBER (II) */
proc sql;
	create table work.examscores_II as
		select *,
			monotonic() as rownumber_II
		from work.examscores;
quit;
The Input Data Set
The Input Data Set
Adding Row Numbers in SAS (Option I)
Adding Row Numbers in SAS (Option I)
Adding Row Numbers in SAS (Option II)
Adding Row Numbers in SAS (Option II)

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