Understanding the SAS/IML Language: Command Statements

Command Statements

Command statements are used to perform specific system actions, such as storing and loading matrices and modules, or to perform special data processing requests. The following table lists some commands and the actions they perform.

Table 3.2 Command Statements
Statement	Description
FREE	Frees memory associated with a matrix
LOAD	Loads a matrix or module from a storage library
MATTRIB	Associates printing attributes with matrices
PRINT	Prints a matrix or message
RESET	Sets various system options
REMOVE	Removes a matrix or module from library storage
SHOW	Displays system information
STORE	Stores a matrix or module in the storage library

These commands play an important role in SAS/IML software. You can use them to control information displayed about matrices, symbols, or modules.

If a certain computation requires almost all of the memory on your computer, you can use commands to store extraneous matrices in the storage library, free the matrices of their values, and reload them later when you need them again. For example, the following statements define several matrices:

proc iml;
a = {1 2 3, 4 5 6, 7 8 9};
b = {2 2 2};
show names;

Figure 3.3 List of Symbols in RAM

 SYMBOL   ROWS   COLS TYPE   SIZE                                               
 ------ ------ ------ ---- ------                                               
 a           3      3 num       8                                               
 b           1      3 num       8                                               
  Number of symbols = 2  (includes those without values)

Suppose that you want to compute a quantity that does not involve the a matrix or the b matrix. You can store a and b in a library storage with the STORE command, and release the space with the FREE command. To list the matrices and modules in library storage, use the SHOW STORAGE command (or the STORAGE function), as shown in the following statements:

store a b;                 /* store the matrices */
show storage;              /* make sure the matrices are saved */
free a b;                  /* free the RAM */

The output from the SHOW STORAGE statement (see Figure 3.4) indicates that there are two matrices in storage. (There are no modules in storage for this example.)

Figure 3.4 List of Symbols in Storage

Contents of storage library = WORK.IMLSTOR                                      
                                                                                
Matrices:                                                                       
A                                B                                              
                                                                                
Modules:

You can load these matrices from the storage library into RAM with the LOAD command, as shown in the following statement:

load a b;

See Chapter 17, Storage Features, for more details about storing modules and matrices.

Data Management Commands

SAS/IML software has many commands that enable you to manage your SAS data sets from within the SAS/IML environment. These data management commands operate on SAS data sets. There are also commands for accessing external files. The following table lists some commands and the actions they perform.

Table 3.3 Data Management Statements
Statement	Description
APPEND	Adds records to an output SAS data set
CLOSE	Closes a SAS data set
CREATE	Creates a new SAS data set
DELETE	Deletes records in an output SAS data set
EDIT	Reads from or writes to an existing SAS data set
FIND	Finds records that satisfy some condition
LIST	Lists records
PURGE	Purges records marked for deletion
READ	Reads records from a SAS data set into IML matrices
SETIN	Sets a SAS data set to be the input data set
SETOUT	Sets a SAS data set to be the output data set
SORT	Sorts a SAS data set
USE	Opens an existing SAS data set for reading

These commands can be used to perform data management. For example, you can read observations from a SAS data set into a target matrix with the USE or EDIT command. You can edit a SAS data set and append or delete records. If you have a matrix of values, you can output the values to a SAS data set with the APPEND command. See Chapter 7, Working with SAS Data Sets, and Chapter 8, File Access, for more information about these commands.