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SAS has long developed software for data analysis, econometrics, operations research, and quality improvement. The purpose of these pages is to provide our users with technical information about using this software, including details about software capabilities, examples, papers, e-newsletter, and communities.

Featured News

Tech Support tip Estimating Nonlinear Combinations of Model Parameters

The NLEstimate macro enables you to estimate one or more linear or nonlinear combinations of parameters from any model for which you can save the model parameters and their variance-covariance matrix. Most modeling procedures that offer ESTIMATE, CONTRAST, or LSMEANS statements provide only for estimating or testing linear combinations of model parameters. However, common estimation problems often involve nonlinear combinations, particularly in generalized models with nonidentity link functions such as logistic and Poisson models. For example, in a logistic model you might want to estimate the difference in probabilities (means) between two groups. A linear contrast only enables you to estimate the difference in log odds from which an odds ratio can be estimated. Estimating the difference in means in any generalized linear model that doesn't use an identity link requires estimating a nonlinear function of the model parameters.

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Fitting Multilevel Hierarchical Mixed Models Using PROC NLMIXED

Hierarchical nonlinear mixed models are complex models that occur naturally in many fields. The NLMIXED procedure's ability to fit linear and nonlinear models with standard or general distributions enables you to fit a wide range of such models. SAS/STATŪ 13.2 enhanced PROC NLMIXED to support multiple RANDOM statements, enabling you to fit nested multilevel mixed models. This paper uses an example to illustrate the new functionality.

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SAS/STAT Users Still Moving to the SAS 9.4 Platform?

Aren't we all! We featured this handout last time, but it's timeless!

If you are moving up to SAS 9.4 and would like to catch up on the recent SAS/STAT releases on that platform, this handout is for you! Get an overview of our new additions in missing data analysis, modern survival data analysis, statistical modeling, spatial point pattern analysis, Bayesian analysis, item response analysis, classification and regression trees, and performance enhancements. There's truly something here for everyone. And if you aren't currently on the move, feel free to use this handout however it helps you get into the passing lane!

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blog image Speaking of Graphics

Distinguished Research Statistician Developer Warren Kuhfeld has written two posts on the Graphically Speaking blog. You can learn about controlling the order of legend entries and the assignment of groups to style elements in PROC SGPLOT and learn how to produce a heat map together with a table, outline select cells, and display multiple values within a cell.