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SAS System
SAS (pronounced "sass", originally Statistical Analysis System) is an integrated system of software products provided by SAS Institute that enables the programmer to perform:
In addition, SAS has many business solutions that enable large scale software solutions for areas such as IT management, human resource management, financial management, business intelligence, customer relationship management and more.
Description of SASSAS is driven by SAS programs that define a sequence of operations to be performed on data stored as tables. Although non-programmer graphical user interfaces to SAS exist (such as the SAS Enterprise Guide), most of the time these GUIs are just a front-end to automate or facilitate generation of SAS programs. SAS components expose their functionalities via application programming interfaces, in the form of statements and procedures. A SAS program is composed of three major parts, the DATA step, procedure steps (effectively, everything that is not enclosed in a DATA step), and a macro language. SAS Library Engines and Remote Library Services allow access to data stored in external data structures and on remote computer platforms. The DATA step section of a SAS program, like other database-oriented fourth-generation programming languages such as SQL or Focus, assumes a default file structure, and automates the process of identifying files to the operating system, opening the input file, reading the next record, opening the output file, writing the next record, and closing the files. This allows the user/programmer to concentrate on the details of working with the data within each record, in effect working almost entirely within an implicit program loop that runs for each record. All other tasks are accomplished by procedures that operate on the data set (SAS' terminology for "table") as a whole. Typical tasks include printing or performing statistical analysis, and may just require the user/programmer to identify the data set. Procedures are not restricted to only one behavior and thus allow extensive customization, controlled by mini-languages defined within the procedures. SAS also has an extensive SQL procedure, allowing SQL programmers to use the system with little additional knowledge. There are macro programming extensions, that allow for rationalization of repetitive sections of the program. Proper imperative and procedural programming constructs can be simulated by use of the "open code" macros or the SAS/IML component. Macro code in a SAS program, if any, undergoes preprocessing. At runtime, DATA steps are compiled and procedures are interpreted and run in the sequence they appear in the SAS program. A SAS program requires the SAS software to run. Compared to general-purpose programming languages, this structure allows the user/programmer to be less familiar with the technical details of the data and how it is stored, and relatively more familiar with the information contained in the data. This blurs the line between user and programmer, appealing to individuals who fall more into the 'business' or 'research' area and less in the 'information technology' area, since SAS does not enforce (although SAS recommends) a structured, centralized approach to data and infrastructure management. SAS runs on IBM mainframes, Unix machines, OpenVMS Alpha, and Microsoft Windows; and code is almost transparently moved between these environments. Older versions have supported PC-DOS, the Apple Macintosh, VMS, VM/CMS, Data General AOS and OS/2. Early history of SASSAS was conceived by Anthony J. Barr in 1966.[1] As a North Carolina State University graduate student from 1962 to 1964, Barr had created an analysis of variance modeling language inspired by the notation of statistician Maurice Kendall, followed by a multiple regression program that generated machine code for performing algebraic transformations of the raw data. Drawing on those programs and his experience with structured data files[2], he created SAS, placing statistical procedures into a formatted file framework. From 1966 to 1968, Barr developed the fundamental structure and language of SAS. In January 1968, Barr and James Goodnight collaborated, integrating new multiple regression and analysis of variance routines developed by Goodnight into Barr's framework.[3][4] Goodnight's routines made the handling of basic statistical analysis more robust, and his later implementation (in SAS 76) of the general linear model greatly increased the analytical power of the system. By 1971, SAS was gaining popularity within the academic community. And by 1972, industry was making use of SAS. One strength of the system was analyzing experiments with missing data, which was useful to the pharmaceutical and agricultural industries, among others. In 1973, John Sall joined the project, making extensive programming contributions in econometrics, time series, and matrix algebra. Other participants in the early years included Caroll G. Perkins, Jolayne W. Service, and Jane T. Helwig. Perkins made programming contributions. Service and Helwig created the early documentation.[3] In 1976, SAS Institute, Inc. was incorporated by Barr, Goodnight, Sall, and Helwig. ComponentsSAS consists of a number of components, which organizations separately license and install as required.
TerminologyWhere many other languages refer to tables, rows, and columns/fields, SAS uses the terms data sets, observations, and variables respectively. This usage derives from its statistical heritage, and is shared by SPSS, another statistical package. There are only two kinds of variables in SAS, numeric and character (string). By default all numeric variables are stored as real. It is possible to reduce precision however. Date and datetime variables are numeric variables that inherit the C tradition and are stored as either the number of days (for date variables) or seconds (for datetime variables) from an epoch of 1960-01-01 00:00:00. Features
Example SAS codeSAS uses data steps and procedures to analyze and manipulate data. By default, a data step iterates through each observation in a data set (like every row in a SQL table). This data step creates a new data set BBB that includes those observations from data set AAA that had charges greater than 100. data BBB;
set AAA(where = (charge > 100));
run;
Procedures that can summarize data are available in SAS. The proc freq procedure shows a frequency distribution of a given variable in a data set. proc freq data=BBB;
table charge;
run;
SAS also allows direct subsetting of rows and/or columns of the data used as input to a procedure. The two previous examples could be replaced by the following: proc freq data=AAA(where = (charge > 100));
table charge;
run;
The same program could produce a data set containing the frequency distribution: ... table charge/out=charge_freq; ... SAS features a macro language, which can be used to generate SAS code. For instance, the above example could be re-used in many pieces of code by rewriting it as a macro: %macro freqtable (table, variable);
proc freq data = &table;
table &variable;
run;
%mend freqtable;
%freqtable (BBB, charge)
SAS also features SQL, which can be used to create, modify or query SAS datasets or external database tables accessed with a SAS libname engine. For example, duplicate records could be extracted from a table for analysis: proc sql;
create table dup_recs
as select *
from your_dataset
group by id
having count(*) > 1
;
quit;
The proc print procedure allows the user to display information in ways not possible using only the SQL SELECT statement. proc print data=BBB; run; SAS features SCL, which can be used to create object oriented programs. SCL programs provide a robust library of features not available in Base/SAS or SAS/Macro. class arrays;
public num supplyChain [*,*,*,*];
eventhandler runInterace / (sender='*', event='prepack for singles and bulk');
runInterface: method;
call send(_self_, 'step1');
call send(_self_, 'step2');
* --- ;
call send(_self_, 'step99');
endmethod;
step1: method / (description='initialize array: suppliers, distro-centers, stores, prepack options');
supplyChain=makearray(34000, 15, 3207, 10);
endmethod;
step2: method / (description='load data');
* code cut;
endmethod;
step99: method / (description='print results');
submit continue;
proc print data=work.results;
run;
endsubmit;
endmethod;
endclass;
Version history
SAS 71SAS 71 was the first limited release of the system. The first manual for SAS was printed at this time, approximately 60 pages long[5]. The DATA step was implemented. Regression and analysis of variance were the main uses of the program. SAS 72This more robust release was the first to achieve wide distribution. It included a substantial user's guide, 260 pages in length[6]. The MERGE statement was introduced in this release, adding the ability to perform a database JOIN on two data sets[7]. This release also introduced the comprehensive handling of missing data[8]. SAS 76SAS 76 was a complete system level rewrite, featuring an open architecture for adding and extending procedures, and for extending the compiler[9]. The INPUT and INFILE statements were significantly enhanced to read virtually all data formats in use on the IBM mainframe[10]. Report generation was added through the PUT and FILE statements[11]. The capacity to analyze general linear models was added[12]. 79.3 - 82.41980 saw the addition of SAS/GRAPH, a graphing component; and SAS/ETS for econometric and time series analysis. In 1981 SAS/FSP followed, providing full-screen interactive data entry, editing, browsing, retrieval, and letter writing. In 1983 full-screen spreadsheet capabilities were introduced (PROC FSCALC). For IBM mainframes, SAS 82 no longer required SAS databases to have direct access organization ( (DSORG=DAU), because SAS 82 removed location-dependent information from databases. This permitted SAS to work with datasets on tape and other media besides disk. Version 4 seriesIn the early 1980s, SAS Institute released Version 4, the first version for non-IBM computers. It was written mostly in a subset of the PL/I language, to run on several minicomputer manufacturers' operating systems and hardware: Data General's AOS/VS, Digital Equipment's VAX/VMS, and Prime Computer's PRIMOS. The version was colloquially called "Portable SAS" because most of the code was portable, i.e., the same code would run under different operating systems. Version 5 seriesVersion 6 seriesVersion 6 represented a major milestone for SAS. While it was superficially similar to the user, the major change was "under the hood", where the software was rewritten. From its FORTRAN origins, followed by PL/I and mainframe assembly language; in version 6 SAS was rewritten in C, to provide enhanced portability between operating systems, as well as access to an increasing pool of C programmers compared to the shrinking pool of PL/I programmers. This was the first version to run on UNIX, MS-DOS and Windows platforms. The DOS versions were incomplete implementations of the Version 6 spec: some functions and formats were unavailable, as were SQL and related items such as indexing and WHERE subsetting. DOS memory limitations restricted the size of some user-defined items. The mainframe version of SAS 6 changed the physical format of SAS databases from "direct files" (DSORG=DA) to "flat files" (DSORG=PS,RECFM=FS). The practical benefit of this change is that a SAS 6 database can be copied from any media with any copying tool. In 1984 a project management component was added (SAS/PROJECT). In 1985 SAS/AF software, econometrics and time series analysis (SAS/ETS) component, and interactive matrix programming (SAS/IML) software was introduced. MS-DOS SAS (version 6.02) was introduced, along with a link to mainframe SAS. In 1986 Statistical quality improvement component is added (SAS/QC software); SAS/IML and SAS/STAT software is released for personal computers. 1987 saw concurrent update access provided for SAS data sets with SAS/SHARE software. Database interfaces are introduced for DB2 and SQL-DS. In 1988 MultiVendor Architecture (MVA) concept is introduced; SAS/ACCESS software is released. Support for UNIX-based hardware announced. SAS/ASSIST software for building user-friendly front-end menus is introduced. New SAS/CPE software establishes SAS as innovator in computer performance evaluation. Version 6.03 for MS-DOS is released. 6.06 for MVS, CMS, and OpenVMS is announced in 1990. The same year, the last MS-DOS version (6.04) is released. Data visualization capabilities added in 1991 with SAS/INSIGHT software. In 1992 SAS/CALC, SAS/TOOLKIT, SAS/PH-Clinical, and SAS/LAB software is released. In 1993 software for building customized executive information systems (EIS) is introduced. Release 6.08 for MVS, CMS, VMS, VSE, OS/2, and Windows is announced. 1994 saw the addition of ODBC support, plus SAS/SPECTRAVIEW and SAS/SHARE*NET components. 6.09 saw the addition of a data step debugger. 6.09E for MVS. 6.10 in 1995 was a Microsoft Windows release and the first release for the Apple Macintosh. Version 6 was the first, and last series to run on the Macintosh. JMP, also produced by the SAS Institute, is the software package the company produces for the Macintosh. Also in 1995, 6.11 (codenamed Orlando) was released for Windows 95, Windows NT, and UNIX. 6.12 were Unix and Microsoft Windows releases (and more?) (Some of the following milestones in this sub-section may belong under version 7 or 8.) In 1996 SAS announces Web enablement of SAS software. Scalable performance data server is introduced. In 1997 SAS/Warehouse Administrator and SAS/IntrNet software goes into production. 1998 sees SAS introduce a customer relationship management (CRM) solution, and an ERP access interface ? SAS/ACCESS interface for SAP R/3. SAS is also the first to release OLE-DB for OLAP and releases HOLAP solution. Balanced scorecard, SAS/Enterprise Reporter, and HR Vision are released. First release of SAS Enterprise Miner. 1999 sees the releases of HR Vision software, the first end-to-end decision-support system for human resources reporting and analysis; and Risk Dimensions software, an end-to-end risk-management solution. MS-DOS versions are abandoned because of Y2K issues and lack of continued demand. In 2000 SAS shipped Enterprise Guide and ported its software to Linux. Version 7 seriesThe Output Delivery System debuted in version 7; as did long variable names (from 8 to 32 characters); storage of long character strings in variables (from 200 to 32,767); and a much improved built-in text editor, the Enhanced Editor. Version 7 saw the synchronisation of features between the various platforms for a particular version number (which previously hadn't been the case). Version 7 was a precursor to version 8. It was believed SAS Institute released a snapshot from their development on version 8 to meet a deadline promise. SAS Institute recommended that sites wait until version 8 before deploying the new software. Version 8 seriesReleased about 1999; 8.0, 8.1, 8.2 were Unix, Microsoft Windows, CMS (z/VM) and z/OS releases. Key features: long variable names, Output Delivery System (ODS). SAS 8.1 was released in 2000. SAS 8.2 was released in 2001. Version 9 seriesIn version 9, SAS Institute added the SAS Management Console, parallel processing, JavaObj, ODS OO (experimental as opposed to alpha), and National Language Support. Again the SAS Institute recommended sites delay deployment until 9.1. SAS Version 9 is running on Windows (32 & 64 bit), Unix (64 bit), Linux, and z/OS. Support for CMS (z/VM) was dropped. SAS 9.1 was released in 2003. SAS 9.1.2 was released in 2004. SAS 9.1.3 was released in 2005. SAS 9.2 is the latest release *9.2 is the only version that works on Microsoft Vista* (March 2008) and was demonstrated at SAS Global Forum (previously called SUGI) 2008http://support.sas.com/events/sasglobalforum/2008/index.html. A list of features added to this release of SAS can be seen at the "What's New in SAS" web pagehttp://support.sas.com/documentation/whatsnew/index.html.
There are several important additions to base SAS in Version 9. The new hash object now allows functionality similar to the MERGE statement without sorting data or building formats. The function library was enlarged, and many functions have new parameters. Perl Regular Expressions are now supported, as opposed to the old "Regular Expression" facility, which was incompatible with most other implementations of Regular Expressions. Long format names are now supported. The most important upgrades in Version 9 are for object-oriented programming in the SAS/AF module. CriticismSAS had been criticized for its relatively poor graphics when compared with other statistical software packages. With the release of the Output Delivery System (ODS) for Statistical Graphics extension in SAS 7, the graphics have improved significantly[14]. Critics also cite the existence of free alternatives (such as DAP and R) that have similar statistics functionality. The development tools provided - which include the Enhanced text editor, log (especially for macro execution), DATA step debugger, SCL debugger - are also outdated compared to what other development environments provide. SAS has overcome most issues surrounding presentation graphics by providing export capabilities for third party packages. While the SAS interface may appear outdated when compared to popular IDE's, it is also noted that many such IDE's have been discontinued and are no longer supported by the vendor. External linksNotesReferences
fr:SAS (langage) it:SAS (linguaggio di programmazione) nl:SAS (programmeertaal) pl:SAS (program) fi:SAS (ohjelmisto) sv:SAS System zh:SAS?? Source: Wikipedia | The above article is available under the GNU FDL. | Edit this article
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