The DO Loop

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Rick WicklinJanuary 21, 2014 0

The best articles of 2013: Twelve posts from The DO Loop that merit a second look

I began 2014 by compiling a list of 13 popular articles from my blog in 2013. Although this "People's Choice" list contains many articles that I am proud of, it did not include all of my favorites, so I decided to compile an "Editor's Choice" list. The blog posts on

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Rick WicklinJanuary 7, 2014 4

13 popular articles from 2013

In 2013 I published 110 blog posts. Some of these articles were more popular than others, often because they were linked to from a SAS newsletter such as the SAS Statistics and Operations Research News. In no particular order, here are some of my most popular posts from 2013, organized

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Rick WicklinDecember 4, 2013 5

Secret Santa: What is the probability that someone pulls her own name from a hat?

Each year my siblings choose names for a Christmas gift exchange. It is not unusual for a sibling to pick her own name, whereupon the name is replaced into the hat and a new name is drawn. In fact, that "glitch" in the drawing process was a motivation for me

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Rick WicklinNovember 25, 2013 7

Twelve advantages to calling R from the SAS/IML language

For several years, there has been interest in calling R from SAS software, primarily because of the large number of special-purpose R packages. The ability to call R from SAS has been available in SAS/IML since 2009. Previous blog posts about R include a video on how to call R

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Rick WicklinNovember 20, 2013 2

Write a reusable SAS/IML module that passes values to R

When I call R from within the SAS/IML language, I often pass parameters from SAS into R. This feature enables me to write general-purpose, reusable, modules that can analyze data from many different data sets. I've previously blogged about how to pass values to SAS procedures from PROC IML by

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Rick WicklinSeptember 30, 2013 16

Generate combinations in SAS

Last week I described how to generate permutations in SAS. A related concept is the "combination." In probability and statistics, a combination is a subset of k items chosen from a set that contains N items. Order does not matter, so although the ordered triplets (B, A, C) and (C,

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Rick WicklinSeptember 25, 2013 1

Compute contours of the bivariate normal CDF

This is the last post in my recent series of articles on computing contours in SAS. Last month a SAS customer asked how to compute the contours of the bivariate normal cumulative distribution function (CDF). Answering that question in a single blog post would have resulted in a long article,

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Rick WicklinSeptember 23, 2013 5

Generate permutations in SAS

I've written several articles that show how to generate permutations in SAS. In the SAS DATA step, you can use the ALLPEM subroutine to generate all permutations of a DATA step array that contain a small number (18 or fewer) elements. In addition, the PLAN procedure enables you to generate

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Rick WicklinJuly 26, 2013 0

How to choose parameters so that a distribution has a specified mean and variance

The truncated normal distribution TN(μ, σ, a, b) is the distribution of a normal random variable with mean μ and standard deviation σ that is truncated on the interval [a, b]. I previously blogged about how to implement the truncated normal distribution in SAS. A friend wanted to simulate data

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Rick WicklinJune 24, 2013 5

Count the number of unique rows in a matrix

How do you count the number of unique rows in a matrix? The simplest algorithm is to sort the data and then iterate down the rows, comparing each row with the previous row. However, this algorithm has two shortcomings: it physically sorts the data (which means that the original locations

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