When
you work with
SAS, you use files that are created and maintained by SAS, as well as files
that are created and maintained by your operating environment, and that are
not related to SAS. Files with formats or structures known to SAS are referred
to as SAS files. All SAS files reside in a SAS data library.
The most commonly used SAS file is a SAS data
set. A SAS data set is structured in a format that SAS can process.
Another common type of SAS file is a SAS catalog. Many
different kinds of information that are used in a SAS job are stored in SAS
catalogs, such as instructions for reading and printing data values, or function
key settings that you use in the SAS windowing environment. A SAS
stored program is a type of SAS file that contains compiled code
that you create and save for repeated use.
Operating Environment Information: In some operating environments, a SAS data library is a physical relationship
among files; in others, it is a logical relationship. Refer to the SAS documentation
for your operating environment for details about the characteristics of SAS
data libraries in your operating environment. ![[cautionend]](../common/images/cautend.gif)
There
are two kinds of SAS data sets:
- SAS data file
- SAS data view.
A SAS data
file both describes and
physically stores your data values. A SAS data view,
on the other hand, does not actually store values. Instead, it is a query
that creates a logical SAS data set that you can use as if it were a single
SAS data set. It enables you to look at data stored in one or more SAS data
sets or in other vendors' software files. SAS data views enable you to create
logical SAS data sets without using the storage space required by SAS data
files.
A SAS data set consists of the following:
- descriptor
information
- data values.
The descriptor information describes the contents of the
SAS data set to SAS. The data values are data that has
been collected or calculated. They are organized into rows, called observations,
and columns, called variables. An observation is a collection
of data values that usually relate to a single object. A variable is the set of data values that describe a given characteristic.
The following figure represents a SAS data set:
![[IMAGE]](./images/01405159.gif)
Usually, an observation is the
data that is associated
with an entity such as an inventory item, a regional sales office, a client,
or a patient in a medical clinic. Variables are characteristics of these entities,
such as sale price, number in stock, and originating vendor. When data values
are incomplete, SAS uses a missing value to represent
a missing variable within an observation.
Data
files that you use to read and write data, but which are in a structure unknown
to SAS, are called external files. External files can
be used for storing
- raw data that you want to read into a SAS data
file
- SAS program statements
- procedure output.
Operating Environment Information: Refer to
the SAS documentation
for your operating environment for details about the characteristics of external
files in your operating environment.
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| Database Management System Files |
SAS software is able to
read and write data to and from
other vendors' software, such as many common database management system (DBMS)
files. In addition to base SAS software, you must license the SAS/ACCESS software
for your DBMS and operating environment.
The SAS language consists
of statements, expressions, options, formats, and functions similar to those
of many other programming languages. In SAS, you use these elements within
one of two groups of SAS statements:
A DATA
step consists of a group of statements
in the SAS language that reads raw data or existing SAS data sets to create
a SAS data set. Once your data is accessible as a SAS data set, you can analyze
the data and write reports by using a set of tools known as SAS procedures.
A group of procedure statements is called a PROC step. SAS procedures
analyze data in SAS data sets to produce
statistics, tables, reports, charts, and plots, to create SQL queries, and
to perform other analyses and operations on your data. They also provide ways
to manage and print SAS files.
You can also use global SAS statements and options outside
of a DATA step or PROC step.
Base
SAS software includes the SAS Macro Facility, a powerful programming tool
for extending and customizing your SAS programs, and for reducing the amount
of code that you must enter to do common tasks. Macros are SAS files that
contain compiled macro program statements and stored text. You can use macros
to automatically generate SAS statements and commands, write messages to the
SAS log, accept input, or create and change the values of macro variables.
For complete documentation, see SAS Macro Language: Reference.
Copyright 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
