Tag: Statistical Programming

Learn SAS
Rick Wicklin 0
What is a CAS-enabled procedure?

I attended a seminar last week whose purpose was to inform SAS 9 programmers about SAS Viya. I could tell from the programmer's questions that some programmers were confused about three basic topics: What are the computing environments in Viya, and how should a programmer think about them? What procedures

Analytics | Programming Tips
Rick Wicklin 0
Crossover and mutation: An introduction to two operations in genetic algorithms

This article uses an example to introduce to genetic algorithms (GAs) for optimization. It discusses two operators (mutation and crossover) that are important in implementing a genetic algorithm. It discusses choices that you must make when you implement these operations. Some programmers love using genetic algorithms. Genetic algorithms are heuristic

Learn SAS
Rick Wicklin 0
Operations on lists in SAS/IML

To get better at something, you need to practice. That maxim applies to sports, music, and programming. If you want to be a better programmer, you need to write many programs. This article provides an example of forming the intersection of items in a SAS/IML list. It then provides several

Analytics | Learn SAS
Rick Wicklin 0
Estimate a bivariate CDF in SAS

This article shows how to estimate and visualize a two-dimensional cumulative distribution function (CDF) in SAS. SAS has built-in support for this computation. Although the bivariate CDF is not used as much as the univariate CDF, the bivariate version is still a useful tool in understanding the probable values of

Programming Tips
Rick Wicklin 0
The probability integral transform

This article uses simulation to demonstrate the fact that any continuous distribution can be transformed into the uniform distribution on (0,1). The function that performs this transformation is a familiar one: it is the cumulative distribution function (CDF). A continuous CDF is defined as an integral, so the transformation is

Analytics | Programming Tips
Rick Wicklin 0
Simulate correlated variables by using the Iman-Conover transformation

Simulating univariate data is relatively easy. Simulating multivariate data is much harder. The main difficulty is to generate variables that have given univariate distributions but also are correlated with each other according to a specified correlation matrix. However, Iman and Conover (1982, "A distribution-free approach to inducing rank correlation among

Analytics | Learn SAS
Rick Wicklin 0
Rank-based scores and tied values

Many nonparametric statistical methods use the ranks of observations to compute distribution-free statistics. In SAS, two procedures that use ranks are PROC NPAR1WAY and PROC CORR. Whereas the SPEARMAN option in PROC CORR (which computes rank correlation) uses only the "raw" tied ranks, PROC NPAR1WAY uses transformations of the ranks,

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