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Research and Statistical Support


SAS Corner

By Dr.Karl Ho, Research and Statistical Support Services Manager

What's new in the upcoming SAS 8.2?

In October 2000 I wrote about the new developments of SAS 8 in RSS Matters. Now, a half-year later, I'm writing about it again. SAS 8e Release 2 will be out shortly, loaded with more procedures and features than anyone could imagine. Buckle up, this is not a bug-fixing upgrade only. Some of the new features will test the limit of your imagination. I know it does mine. For instance, sending http://www.unt.edu/benchmarks/archives/2000/october00/rss.htm via a SAS program. That's right, you will be able to send E-mail via SMTP (Simple Mail Transfer Protocol) within a SAS program by selecting E-mail addresses from a large address database (so be prudent in hitting that F3 key next time). How about supporting Chinese or Japanese SAS codes and data? Or converting your output directly to your Web server, or in postscript, RTF and PDF files? It does that, and more!

New Features

Here are some new features that caught my eye:

  • Supporting a genuine 64-bit platform

Namely, Sun's Solaris 7, IBM's AIX 4.3 and HP-UX 11.0. This enhancement enables researchers to take advantage of the 64-bit features (such as processing files larger than 2 gb) both at our UNIX research machine sol and the new software. While this has yet to be tested, we are keeping our fingers crossed on how much we can benefit from this technology. That said, we can say we have the capability to do it, can't we?

  • Linux support

The long-awaited Linux version of SAS finally comes into production. We are still in the process of acquiring this new platform for SAS. But before long, researchers on campus will enjoy using a server combining the open-source operating system and SAS. A raincheck is in order! 

  • More on output

The Version 8 Output Delivery System adds more versatility to SAS output. Release 8.2 includes output destinations such as RTF (enhanced), PDF (now production) and XML (enhanced experimental). In addition, new ActiveX/Java-enabled interactive graphs enhance data visualization when output is ported to the Web. Graph'N Go is an example that exports charts loaded with Active X features (read SAS Corner in February 2001)

  • New Statistical procedures

Last but not least, something all researchers are most looking forward to: what new stats can SAS 8.2 do. Well, some of the experimental procedures in 8.1 are fully implemented or in stable mode. Among them:

  • GAM (Generalized Additive Model)

GAM is not new, both to statisticians and SAS developers.  Hastie and Tibshirani proposed in 1990 the modeling technique that estimates an additive approximation to the multivariate regression function, to a broader range of distributional families on top of the conventional linear function. GAM models allow the mean of the dependent variable to depend on an additive predictor through a nonlinear link function such as Logit or Loess. Besides providing the user with the flexibility of nonparametric regression, generalized additive models also have the advantage of easy interpretability, which comes from modeling the regression surface as a sum of smooth terms. GAM procedures are available in S-Plus and other packages as early as in the mid-1990s. SAS 8.1 has this procedure, PROC GAM, in experimental mode. The new release will have it in production.

  • Missing Values Analysis

Another widely studied topic, Missing Values analysis poses as a significant addition to tools for researchers using SAS.   The easiest and most common method of dealing with missing values is to ignore or delete them. While convenient and simple to implement, researchers will lose information about if systematic missing value patterns exist. Above all, precious information from those cases which happen to have one or a few missing values will also be discarded.  

To deal with this problem, statisticians have proposed many ways to "patch the holes in the data." One of them is imputation, or plugging in values to the missing value cases.  Mean or median can do the job but usually not desirable because of the lack of underlying rationale that mean or any moment is  good enough. Rubin suggested in 1976 the multiple imputation method by replacing each missing value with a set of plausible values that represent the "uncertainty" of the real value of interest. Models with imputed values are then estimated and combined to draw inference. SAS 8.1 is equipped with two new procedures, PROC MI and PROC MIANALYZE, to perform this task. In the new release, these two procedures will be in a second experimental release.

When can we get it?

SAS claims the software will be available in mid-March via Web request. The conservative RSS estimate, however, is that it will not be in our hands until late-April. Faculty members should keep checking with us if they are eager to test the new software. As for students, I will certainly make student versions available as soon as possible.  

Bye for now . . .

By the way, RSS wishes you a nice and safe spring break and happy computing.

References

SAS Institute. 2001. What's New in SAS Software for Release 8.2 (http://www.sas.com/products/sassystem/release82/index.html)

Hastie, T.J. and Tibshirani, R.J. (1990), Generalized Additive Models, New York: Chapman and Hall.

Rubin, D.B. (1976), "Inference and Missing Data," Biometrika, 63, 581 -592.

Rubin, D.B. (1987), Multiple Imputation for Nonresponse in Surveys, New York: John Wiley & Sons, Inc.