Posts Tagged ‘ Statistical Programming ’

Test for the equality of two proportions in SAS

July 5, 2017
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Test for the equality of two proportions in SAS

A SAS customer asked how to use SAS to conduct a Z test for the equality of two proportions. He was directed to the SAS Usage Note "Testing the equality of two or more proportions from independent samples." The note says to "specify the CHISQ option in the TABLES statement

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Video: Create and use lists and tables in SAS/IML

June 26, 2017
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My presentation at SAS Global Forum 2017 was "More Than Matrices: SAS/IML Software Supports New Data Structures." The paper was published in the conference proceedings several months ago, but I recently recorded a short video that gives an overview of using the new data structures in SAS/IML 14.2: If your

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Two ways to compute maximum likelihood estimates in SAS

June 14, 2017
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Two ways to compute maximum likelihood estimates in SAS

In a previous article, I showed two ways to define a log-likelihood function in SAS. This article shows two ways to compute maximum likelihood estimates (MLEs) in SAS: the nonlinear optimization subroutines in SAS/IML and the NLMIXED procedure in SAS/STAT. To illustrate these methods, I will use the same data

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Quadratic optimization in SAS

April 12, 2017
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Quadratic optimization in SAS

At SAS Global Forum last week, I saw a poster that used SAS/IML to optimized a quadratic objective function that arises in financial portfolio management (Xia, Eberhardt, and Kastin, 2017). The authors used the Newton-Raphson optimizer (NLPNRA routine) in SAS/IML to optimize a hypothetical portfolio of assets. The Newton-Raphson algorithm

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A simple trick to construct symmetric intervals

April 10, 2017
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A simple trick to construct symmetric intervals

Many intervals in statistics have the form p ± δ, where p is a point estimate and δ is the radius (or half-width) of the interval. (For example, many two-sided confidence intervals have this form, where δ is proportional to the standard error.) Many years ago I wrote an article

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Nonsmooth models and spline effects

April 5, 2017
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Nonsmooth models and spline effects

Most regression models try to model a response variable by using a smooth function of the explanatory variables. However, if the data are generated from some nonsmooth process, then it makes sense to use a regression function that is not smooth. A simple way to model a discontinuous process in

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Print tables in SAS/IML

April 3, 2017
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Print tables in SAS/IML

One of the advantages of the new mixed-type tables in SAS/IML 14.2 is the greatly enhanced printing functionality. You can control which rows and columns are printed, specify formats for individual columns, and even use templates to completely customize how tables are printed. Printing a table is accomplished by using

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Lists: Nonmatrix data structures in SAS/IML

March 29, 2017
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Lists: Nonmatrix data structures in SAS/IML

Lists are collections of objects. SAS/IML 14.2 supports lists as a way to store matrices, data tables, and other lists in a single object that you can pass to functions. SAS/IML lists automatically grow if you add new items to them and shrink if you remove items. You can also

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