SAS/Basics
< SAS
Why use SAS ?
[edit | edit source]- SAS works directly on the data sets without loading them into memory. This allows you to manipulate large database such as census data sets.
Why not use SAS ?
[edit | edit source]- SAS is not available for mac users
- SAS is proprietary and expensive. You may prefer R which is open-source and cross-platforms.
- There is no systematic syntax. The syntax is specific to each PROC.
Alternative to SAS
[edit | edit source]- R : an open source statistical package
- Stata : includes the very latest econometric methods
- SPSS : an easy to use statistical software
SAS Environment
[edit | edit source]- EDITOR (F5)
- This is a text editor with syntax highlighting where you write your program. You can save your program with the .sas extension.
- LOG (F6)
- includes all information about the computing process such as errors, warnings, computing time (cpu). You can save it with the .log extension.
- OUTPUT (F7)
- This includes all the results. You can save it with the .lst extension.
- EXPLORER (CTRL D)
- browse all your SAS libraries and open datasets in the SAS data editor.
- HELP (F1)
- Help system.
SAS Programming Style
[edit | edit source]- SAS includes procedures and data step. data steps generally create a new dataset and procedure step compute some quantity of interest using existing data.
- Each step is ended with the run ; statement.
- Semicolons ; are end of statement delimiter.
- SAS works directly on a database without loading it into memory. This facilitates manipulation of large databases.
- F3 executes the current program or the selected lines of the program.
- After executing a program, you first look at your log and then you can have a look at your results.
- Comments begin with a star and terminated by a semicolon or are contained within a slash-star and a star-slash c-style block comment:
* This is a comment ;
/*This is also a comment */
- SAS is not case sensitive ("a" and "A" are similar to SAS)
Preamble
[edit | edit source]The following lines are often useful at the beginning of a SAS program :
- Libname : It is often useful to defines libname. A libname is nothing more than an alias for a directory.
libname lib_name 'c:/data/ee';
- Options : the following line in head of a program makes it easier to read the log.
options errors=1 noovp pageno=1 ls=78;
- Clean log and output windows : At the beginning of a program it is often convenient to clean the log and the output:
dm "CLEAR LOG ; CLEAR OUTPUT ; " ;
dm stands for "Display Manager"