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[分享]How SAS® Thinks Neil Howard, Basking Ridge, NJ

ABSTRACT

The DATA step is the most powerful tool in the SAS system.  Understanding the internals of DATA step processing,
what is happening and why, is crucial in mastering code and output.  Concepts covered:
•  Logical Program Data Vector (LPDV or PDV),  
•  automatic SAS variables and how they are used,  
•  the importance of understanding the internals of DATA step processing,  
•  what happens at program compile time,  
•  what's happening at execution time,  
•  how variable attributes are captured and stored, and
•  handling processing defaults, data defaults, data conversions, and missing values.   

This workshop focuses on techniques that capitalize on the power of the DATA step and working with (and around)
the default actions.   By understanding DATA step processing, you can debug your programs and interpret your
results with confidence.
INTRODUCTION

SAS procedures are powerful and easy to use, but the DATA step offers the programmer a tool with almost unlimited
potential. In the real world, we’re lucky if systems are  integrated, data is clean and system interfaces are seamless.
The DATA step can help you, your programmers, your program, and your users perform better in the real world –
especially when you take advantage of  the available features.  This paper focuses on basic techniques that
demonstrate the functioning of the DATA step and illustrate the default actions.  Any of the topics/examples covered
in this presentation have more than  enough details, idiosyncrasies, and caveats to warrant its own tutorial, so
selected essential processing tips and illustrative examples are provided: