Posts Tagged ‘ Statistical Programming ’

The path of zip codes

September 18, 2017
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The path of zip codes

Toe bone connected to the foot bone, Foot bone connected to the leg bone, Leg bone connected to the knee bone,...              — American Spiritual, "Dem Bones" Last week I read an interesting article on Robert Kosara's data visualization blog. Kosara connected the geographic centers of the US zip codes in [...] The post The path of zip codes appeared first on The DO Loop.

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Use a bar chart to visualize pairwise correlations

August 16, 2017
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Use a bar chart to visualize pairwise correlations

Visualizing the correlations between variables often provides insight into the relationships between variables. I've previously written about how to use a heat map to visualize a correlation matrix in SAS/IML, and Chris Hemedinger showed how to use Base SAS to visualize correlations between variables. Recently a SAS programmer asked how [...] The post Use a bar chart to visualize pairwise correlations appeared first on The DO Loop.

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Robust principal component analysis in SAS

August 9, 2017
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Robust principal component analysis in SAS

Recently, I was asked whether SAS can perform a principal component analysis (PCA) that is robust to the presence of outliers in the data. A PCA requires a data matrix, an estimate for the center of the data, and an estimate for the variance/covariance of the variables. Classically, these estimates [...] The post Robust principal component analysis in SAS appeared first on The DO Loop.

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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 [...] The post Test for the equality of two proportions in SAS appeared first on The DO Loop.

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

June 26, 2017
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Video: Create and use lists and tables in SAS/IML

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 [...] The post Video: Create and use lists and tables in SAS/IML appeared first on The DO Loop.

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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 [...] The post Two ways to compute maximum likelihood estimates in SAS appeared first on The DO Loop.

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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 [...] The post Quadratic optimization in SAS appeared first on The DO Loop.

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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 [...] The post A simple trick to construct symmetric intervals appeared first on The DO Loop.

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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 [...] The post Nonsmooth models and spline effects appeared first on The DO Loop.

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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 (released with SAS 9.4m4) 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 [...] The post Print tables in SAS/IML appeared first on The DO Loop.

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