A zipper plot for visualizing coverage probability in simulation studies

March 26, 2018
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A zipper plot for visualizing coverage probability in simulation studies

Simulation studies are used for many purposes, one of which is to examine how distributional assumptions affect the coverage probability of a confidence interval. This article describes the "zipper plot," which enables you to compare the coverage probability of a confidence interval when the data do or do not follow

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SAS introduces the blended classroom

March 23, 2018
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We all have different learning styles. Some learn best by seeing and doing; others by listening to lectures in a traditional classroom; still others simply by diving in and asking questions along the way. Traditional face-to-face classroom instruction,...
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Tracking the International Space Station

March 21, 2018
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As we get into springtime weather where I live (assuming it stops snowing today!), I'm planning to spend more time outdoors paying attention to the night sky. There are lots of cool apps these days to help you identify constellations, and track things ...
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The conjugate gradient method

March 21, 2018
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The conjugate gradient method

I often claim that the "natural syntax" of the SAS/IML language makes it easy to implement an algorithm or statistical formula as it appears in a textbook or journal. The other day I had an opportunity to test the truth of that statement. A SAS programmer wanted to implement the

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Compute with combinations: Maximize a function over combinations of variables

March 19, 2018
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Compute with combinations: Maximize a function over combinations of variables

About once a month I see a question on the SAS Support Communities that involves what I like to call "computations with combinations." A typical question asks how to find k values (from a set of p values) that maximize or minimize some function, such as "I have 5 variables,

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Visualize repetition in song lyrics

March 14, 2018
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Visualize repetition in song lyrics

One of my favorite magazines, Significance, printed an intriguing image of a symmetric matrix that shows repetition in a song's lyrics. The image was created by Colin Morris, who has created many similar images. When I saw these images, I knew that I wanted to duplicate the analysis in SAS!

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Where are opioids prescribed most, in North Carolina?

March 12, 2018
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My buddy Rick Wicklin recently pointed me towards an animation of some opioid prescription rate data for Illinois. And, of course, I decided we needed a similar animation for North Carolina (with a few improvements...) Here's the original, and here are...
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Pi, special functions, and distributions

March 12, 2018
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Pi, special functions, and distributions

Welcome to my annual Pi Day post. Every year on March 14th (written 3/14 in the US), geeky mathematicians and their friends celebrate "all things pi-related" because 3.14 is the three-decimal approximation to pi. Pi is a mathematical constant that never changes. Pi is the same value today as it

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Fit a distribution from quantiles

March 7, 2018
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Fit a distribution from quantiles

Data analysts often fit a probability distribution to data. When you have access to the data, a common technique is to use maximum likelihood estimation (MLE) to compute the parameters of a distribution that are "most likely" to have produced the observed data. However, how can you fit a distribution

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