What’s New in SAS/IML 12.1

Overview

In previous years, SAS/IML software was updated only with new releases of Base SAS^®software, but this is no longer the case. This means that SAS/IML software can be released to customers when enhancements are ready, and the goal is to update SAS/IML every 12 to 18 months. To mark this newfound independence, the release numbering scheme for SAS/IML is changing with this release. This new numbering scheme will be maintained when new versions of Base SAS and SAS/IML ship at the same time. For example, when Base SAS 9.4 is released, SAS/IML 13.1 will be released.

SAS/IML 12.1 includes the following changes and enhancements:

a new syntax for defining default parameter values in user-defined modules
a new syntax for reading and writing SAS data sets whose names are not known until run time
new statistical functions, subroutines, and modules
support for additional distributions and parameters for generating random samples by using the RANDGEN subroutine

Enhancements to the SAS/IML Syntax

SAS/IML 12.1 includes the following enhancements to the syntax:

SAS/IML supports a new syntax that defines optional arguments and default parameter values for user-defined modules. One implication of the new syntax is that you cannot omit a parameter when you call a user-defined subroutine unless the module definition explicitly specifies that the parameter is optional. This syntax change might require that you modify SAS/IML programs that parsed and ran without error in previous releases.
There is a new syntax for reading and writing SAS data sets that enables you to read data sets whose name is given by a run-time expression rather than by a literal value. For example, the following syntax is now valid:
```
dsname = "Sashelp.Class"; 
use (dsname); 
read all var _NUM_ into X; 
close (dsname);
```
This syntax is equivalent to the following statements:
```
use Sashelp.Class; 
read all var _NUM_ into X; 
close Sashelp.Class;
```
This functionality is available in the CLOSE, CREATE, EDIT, SETIN, SETOUT, SORT, and USE statements.
You can now pass the same matrix into a module in several parameter locations. The first time that a variable is passed, it is passed by reference. Subsequent arguments receive a copy of the matrix. For example, the following syntax is now valid:
```
start DotProduct(x,y);
    return( x`*y ); 
finish;  

x = {1,2,3,4}; 
z = DotProduct(x, x); /* pass the same matrix twice */ 
```
There is a new syntax for defining an assignment to an empty matrix. The statement x={}; is similar to using the FREE statement. This syntax can be used to specify that the default value of a module argument is the empty matrix.

In addition, SAS/IML 12.1 includes the following enhancements to functions, subroutines, and modules:

The RANDGEN subroutine now accepts vectors of parameters. These vectors can be used to fill a matrix with random values such that each column (or row) of the matrix is sampled from a different distribution.
The ROOT function now accepts an optional parameter that you can use to determine whether a matrix is positive definite.
The SUBSTR function now accepts any parameter as a vector. These vectors can be used to extract several substrings from a string with a single call.

New Functions, Subroutines, and Modules

DIMENSION Function

The DIMENSION function returns a $Inline Graphic of: $1\times 2$$ vector whose elements are the number of rows and columns, respectively, of a matrix.

DISTANCE Function

The DISTANCE function computes pairwise distances betweens rows of a matrix.

FROOT Function

The FROOT function finds zeros of a univariate function by using a numerical root-finding method.

ISSKIPPED Function

The ISSKIPPED function enables you to determine whether an optional argument to a user-defined module was skipped when the module was called.

MAHALANOBIS Function

The MAHALANOBIS function computes the Mahalanobis distance between observations. This function is part of the IMLMLIB library of modules.

NDX2SUB Function

The NDX2SUB function converts the indices of a matrix into subscripts. This function is part of the IMLMLIB library of modules.

NORM Function

The NORM function computes the vector or matrix norm of its argument.

RANPERK Function

The RANPERK function returns a random permutation of Inline Graphic of: $k$

elements from a finite set of Inline Graphic of: $n$

elements, $Inline Graphic of: $k\leq n$$ .

SAMPLE Function

The SAMPLE function generates a random sample of a finite set.

SUB2NDX Function

The SUB2NDX function converts the subscripts of a matrix into indices. This function is part of the IMLMLIB library of modules.