SAS Program Syntax

Overview

This document provides general guidelines for writing SAS programs.

The SAS Command File
Basic Syntax Rules
The Data Step
SAS PROCs (Procedures)
Miscellaneous Statements

The SAS Command File

SAS programs are divided into DATA steps and PROCs. The purpose of the data step is to create one or more SAS data sets. The data step contains statements which read in raw data files or existing SAS data sets. Other data step tasks include transforming, creating, and selecting variables, selecting cases, defining missing data, and providing labels for variables. The data step begins with the word DATA followed by the name of a data set. See Sample Program #1 for an example of a simple data step.

SAS PROCs are used to analyze or graph data or provide information about a SAS data set. For example, PROC REG performs multiple regression on sample data, while PROC CONTENTS tells the user the name and location of the variables in a SAS data set.

A SAS program may contain one or more data steps and/or one or more procedures.

The following texts provide useful information for writing your SAS program:

Online Documentation from SAS Institute.
The Little SAS Book: a primer by Lora D. Delwiche and Susan J. Slaughter (Cary, NC: SAS Institute).
Applied Statistics and the SAS Programming Language, by Cody and Smith

Basic Syntax Rules

The SAS data step consists of a series of statements. Rules for writing these statements follow.

Words:

Words in statements must be separated by one or more blanks.
A word may not be split between lines.
Words may be in upper, lower, or mixed case.
Values of character variables must match data values exactly (case-sensitive).

Variable names:

Variable names must be 32 or fewer characters in length.
All variable names must begin with an alphabetic character (A-Z, a-z) or an underscore (_). Subsequent characters may include digits.
A variable list such as V1-V5 means V1, V2, V3, V4, and V5.
SAS matches variable names precisely character-wise, but not case-wise. That is, V1 is not the same as V01, but V1 is the same as v1.
Variable names may not contain embedded blanks. V1 and V_1 are acceptable; V 1 is not.
Certain names are reserved for use by SAS, e.g., _N_, _TYPE_, and _NAME_. Similarly, logical operators such as ge, lt, and, and eq should not be used as variable names.

Statements:

A statement may begin anywhere on a line and may be continued on additional lines as necessary.
Statements end with a semicolons (;).
Statements which beginning with an asterisk (*) are treated as comments and are not interpreted. A comment is concluded with a semicolon.
A group of statements preceded by /* are ignored until */ is read (block comment). Semicolons between the /* ... */ have no effect.
Multiple statements may appear on a line; they must be separated by semicolons.

The Data Step

The data step begins with the word DATA followed by a name for the temporary or permanent data set to be output by the data step. See theExamples page for sample programs which create and use temporary and permanent SAS data sets.
The data step includes instructions about where to find the data and how to read the values from the data file. For more details, see the page on Data Files in SAS.
The data step may contain instructions to create new variables or transform existing variables, label variables, and select cases or variables. The following statements are examples of valid statements for the SAS data step:
```
    y = sum(of x1-x15) ;
    label y = 'total score' ;
    if y > 10 then group = 1 ;
      else group = 2 ;
    keep group y ;
```
To refer to a missing value for a numeric variable, use a ".". For example the statement if a = 99 then a = . ; forces SAS to treat a value of 99 as if it were missing.
The data step is terminated when SAS encounters the word PROC (signifying the beginning of a SAS Procedure) or finds the words DATALINES ; or CARDS ; (indicating inline data following).
All data step commands must be contained within the data step itself; additional data step commands may only be inserted after a PROC after beginning a new data step and reading in the default data set.

SAS PROCS

SAS PROCs (procedures) are used for many purposes including carrying out statistical analysis (e.g., PROC ANOVA, PROC MEANS), displaying information about a SAS data set (e.g., PROC CONTENTS, PROC PRINT), and creating graphs (PROC GPLOT).
Most PROCs produce output of some kind. The output of statistical PROCs usually appears in the listing file. The output of graphics PROCs often takes the form of a graphics file or graphics stream output to the screen.
The PROC(s) must appear after a data step which creates the SAS data set used in the procedure.
The word PROC automatically terminates a SAS data step.
Data step commands may not appear after a PROC unless a new data step is initiated with the word DATA.
A SAS PROC begins with word PROC followed by the name of the specific procedure (e.g., PROC REG).
Some PROCs have options or subcommands which allow the user to output information into a SAS data set (e.g., PROC MEANS, PROC REG).
The default data set used by a PROC is the data set created by the last data step or PROC before the current PROC. To change the data set used by a PROC, use the DATA= option on the PROC line.

Miscellaneous Commands