Writing Flexible Code with theSAS Macro Facility精选.pdfVIP

CHAPTER 7 Writing Flexible Code with the SAS Macro Facility 7.1 Macro Concepts 210 7.2 Substituting Text with Macro Variables 212 7.3 Creating Modular Code with Macros 214 7.4 Adding Parameters to Macros 216 7.5 Writing Macros with Conditional Logic 218 7.6 Writing Data-Driven Programs with CALL SYMPUT 220 7.7 Debugging Macro Errors 222 210 The Little SAS Book 7.1 Macro Concepts Not so long ago the SAS macro facility was considered an advanced topic relevant only to experienced SAS users. Over time, however, macros have become more prevalent so that now even new SAS users would do well to know a little about the SAS macro facility. Fortunately, the basic macro concepts are not difficult to understand. This chapter introduces the most commonly used features of the SAS macro language. Because macros take longer to write and debug than standard SAS code, you generally won’t want macros in programs that will be run only a few times. But used properly, macros can make the development and maintenance of production programs much easier. They do this in several ways. First, with macros you can make one small change in your program and have SAS echo that change throughout your program. Second, macros allow you to write a piece of code once and use it over and over, in the same program or in different programs. You can even store programs in a central location—an autocall library—and share them between programs and between programmers. Third, you can make your programs data driven, letting SAS decide what to do based on actual data values. The macro processor When you submit a standard SAS pr