Macro Variables Defined by Users

You can create your own macro variables, change their values, and define their scope. You can define a macro variable within a macro, and you can also specifically define it as a global variable, by defining it with the %GLOBAL statement. Macro variable names must start with a letter or an underscore and can be followed by letters or digits. You can assign any name to a macro variable as long as the name is not a reserved word. The prefixes AF, DMS, SQL, and SYS are not recommended because they are frequently used in SAS software when creating macro variables. Thus, using one of these prefixes can cause a name conflict with macro variables created by SAS software. For a complete list of reserved words in the macro language, see Reserved Words in the Macro Facility. If you assign a macro variable name that is not valid, an error message is printed in the SAS log.

You can use %PUT _ALL_ to view all user-created macro variables.

The simplest way to create and assign a value to a macro variable is to use the macro program statement %LET:

%let dsname=Newdata;

DSNAME is the name of the macro variable. Newdata is the value of the macro variable DSNAME. The value of a macro variable is simply a string of characters. The characters can include any letters, numbers, or printable symbols found on your keyboard, and blanks between characters. The case of letters is preserved in a macro variable value. Some characters, such as unmatched quotation marks, require special treatment, which is described later.

If a macro variable already exists, a value assigned to it replaces its current value. If a macro variable or its value contains macro triggers (% or &), the trigger is evaluated before the value is assigned. In the following example, &name is resolved to Cary and then it is assigned as the value of city in the following statements:

%let name=Cary;
%let city=&name;

Generally, the macro processor treats alphabetic characters, digits, and symbols (except & and %) as characters. It can also treat & and % as characters using a special treatment, which is described later. It does not make a distinction between character and numeric values as the rest of SAS does. (However, the %EVAL Function and %SYSEVALF Function can evaluate macro variables as integers or floating point numbers.)

Macro variable values can represent text to be generated by the macro processor or text to be used by the macro processor. Values can range in length from 0 to 65,534 characters. If you omit the value argument, the value is null (0 characters). By default, leading and trailing blanks are not stored with the value.

In addition to the %LET statement, the following list contains other features of the macro language that create macro variables:

• iterative %DO statement

• %GLOBAL statement

• %INPUT statement

• INTO clause of the SELECT statement in SQL

• %LOCAL statement

• %MACRO statement

• SYMPUT routine and SYMPUTN routine in SCL

• %WINDOW statement

The following table describes how to assign a variety of types of values to macro variables.

%let street=maple;

%let street=            maple;
%let street=maple            ;

%let num=123;
%let totalstr=100+200;

%let num=%eval(100+200); / * produces 300 * /

%let num=%sysevalf(100+1.597); / * produces 101.597 * /

%let country=;

%let street=Maple;
%let num=123;
%let address=&num &street Avenue;

%let status=%wait;

%let status=%nrstr(%wait);

%let state=%str( North Carolina);
%let town=%str(Taylor%'s Pond);
%let store=%nrstr(Smith&Jones);
%let plotit=%str(
       proc plot;
         plot income*age;
       run;);

data _null_;
   set in.permdata end=final;
   if age>20 then n+1;
   if final then call symput('number',trim(left(n)));
run;
footnote "&number Observations have AGE>20";

Copyright © 2009 by SAS Institute Inc., Cary, NC, USA. All rights reserved.