SAS Macro Language: Reference

More Advanced Macro Techniques

After mastering the basic techniques discussed earlier in this chapter, you may want to learn some more advanced macro techniques.

Generating Repetitive Pieces of Text Using %DO Loops

Conditionally Generating SAS Code presents a %DO-%END group of statements to conditionally execute several SAS statements. To generate repetitive pieces of text, use an iterative %DO loop. For example, the following macro, NAMES, uses an iterative %DO loop to create a series of names to be used in a DATA statement.:

%macro names(name= ,number= );
   %do n=1 %to &number;
      &name&n
   %end;
%mend names;

The macro NAMES creates a series of names by concatenating the value of the parameter NAME and the value of the macro variable N. You supply the stopping value for N as the value of the parameter NUMBER, as in the following DATA statement:

data %names(name=dsn,number=5);

Submitting this statement produces the following complete DATA statement:

data dsn1 dsn2 dsn3 dsn4 dsn5;

Note: You can also execute a %DO loop conditionally with %DO %WHILE and %DO %UNTIL statements. See Chapter 13 for details on these statements. [cautionend]

Generating a Suffix for a Macro Variable Reference

Suppose that, when you generate a numbered series of names, you always want to put the letter X between the prefix and the number. The macro NAMESX inserts an X after the prefix you supply:

%macro namesx(name=,number=);
   %do n=1 %to &number;
      &name.x&n
   %end;
%mend namesx;

The period is a delimiter at the end of the reference &NAME. The macro processor uses the delimiter to distinguish the reference &NAME followed by the letter X from the reference &NAMEX. Here is an example of calling the macro NAMESX in a DATA statement:

data %namesx(name=dsn,number=3);

Submitting this statement produces the following statement:

data dsnx1 dsnx2 dsnx3;

See Chapter 3, "Macro Variables," for more information about using a period as a delimiter in a macro variable reference.

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