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Rick WicklinJanuary 26, 2022 3

4 ways to find the k smallest and largest data values in SAS

Sometimes it is useful to know the extreme values in data. You might need to know the Top 5 or the Top 10 smallest data values. Or, the Top 5 or Top 10 largest data values. There are many ways to do this in SAS, but this article shows examples

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Analytics | Learn SAS | Programming Tips

Rick WicklinJanuary 24, 2022 0

Estimate percentiles in SAS Viya

How can you estimate percentiles in SAS Viya? This article shows how to call the percentile action from PROC CAS to estimate percentiles of variables in a CAS data table. Percentiles and quantiles are essentially the same (the pth quantile is the 100*pth percentile for p in [0, 1]), so

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Programming Tips

Rick WicklinJanuary 20, 2022 6

How often do different statistical tests agree? A simulation study

Here's a fun problem to think about: Suppose that you have two different valid ways to test a statistical hypothesis. For a given sample, will both tests reject or fail to reject the hypothesis? Or might one test reject it whereas the other does not? The answer is that two

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Learn SAS | Programming Tips

Rick WicklinJanuary 18, 2022 0

Simulate events when some probabilities are zero

Several probability distributions model the outcomes of various trials when the probabilities of certain events are given. For some distributions, the definitions make sense even when a probability is 0. For other distributions, the definitions do not make sense unless all probabilities are strictly positive. This article examines how zero

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Programming Tips

Rick WicklinJanuary 12, 2022 3

How to assign a name to a color

Some colors have names, such as "Red," "Magenta," and "Dark Olive Green." But the most common way to specify a color is to use a hexadecimal value such as CX556B2F. It is not obvious that "Dark Olive Green" and CX556B2F represent the same color, but they do! I like to

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Analytics | Learn SAS | Programming Tips

Rick WicklinJanuary 10, 2022 0

12 blog posts from 2021 that deserve a second look

On this blog, I write about a diverse set of topics that are relevant to statistical programming and data visualization. In a previous article, I presented some of the most popular blog posts from 2021. The most popular articles often deal with elementary or familiar topics that are useful to

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Programming Tips

Rick WicklinJanuary 5, 2022 0

A block-Cholesky method to simulate multivariate normal data

You can use the Cholesky decomposition of a covariance matrix to simulate data from a correlated multivariate normal distribution. This method is encapsulated in the RANDNORMAL function in SAS/IML software, but you can also perform the computations manually by calling the ROOT function to get the Cholesky root and then

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Analytics | Data Visualization | Programming Tips

Rick WicklinJanuary 3, 2022 3

Top 10 posts from The DO Loop in 2021

Last year, I wrote almost 100 posts for The DO Loop blog. My most popular articles were about data visualization, statistics and data analysis, and simulation and bootstrapping. If you missed any of these gems when they were first published, here are some of the most popular articles from 2021:

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Analytics | Programming Tips

Rick WicklinDecember 6, 2021 1

The expected number of points on a convex hull

While discussing how to compute convex hulls in SAS with a colleague, we wondered how the size of the convex hull compares to the size of the sample. For most distributions of points, I claimed that the size of the convex hull is much less than the size of the

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Learn SAS | Programming Tips

Rick WicklinNovember 29, 2021 5

Caslibs and librefs in SAS Viya

When SAS 9 programmers transition to SAS Viya, there are inevitably questions about how new concepts in Cloud Analytic Services (CAS) relate to similar concepts in SAS. This article discusses the question, "What is the difference between a libref and a caslib?" Both are used to access data, but they

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