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Rick Wicklin 0
Simulate categorical data in SAS

As I was reviewing notes for my course "Data Simulation for Evaluating Statistical Methods in SAS," I realized that I haven't blogged about simulating categorical data in SAS. This article corrects that oversight. An Easy Way and a Harder Way SAS software makes it easy to sample from discrete "named"

Chris Hemedinger 0
SAS 9.3: the list

Alison posted the Top 10 Reasons you should care about SAS 9.3. It's a bit tongue-in-cheek, but it reflects just a sample of the thousands of features and tweaks that you'll see in this new release. Even with SAS 9.2, I was nowhere near exhausting my backlog of blog topics...but

Programming Tips
Chris Hemedinger 0
Computing age in SAS 9.3

It seems like such a simple problem: how can you reliably compute the age of someone or something? Susan lamented the subtle issues using the YRDIF function exactly 1.0356164384 years ago. Sure, you could write your own function for calculating such things, as I suggested 0.1753424658 years ago. Or you

Rick Wicklin 0
Improving graphs of highly correlated data

If you create a scatter plot of highly correlated data, you will see little more than a thin cloud of points. Small-scale relationships in the data might be masked by the correlation. For example, Luke Miller recently posted a scatter plot that compares the body temperature of snails when they

Rick Wicklin 0
Add a diagonal line to a scatter plot

In my statistical analysis of coupons article, I presented a scatter plot that includes the identity line, y=x. This post describes how to write a general program that uses the SGPLOT procedure in SAS 9.2. By a "general program," I mean that the program produces the result based on the

Rick Wicklin 0
The area under a density estimate curve

Readers' comments indicate that my previous blog article about computing the area under an ROC curve was helpful. Great! There is another common application of numerical integration: finding the area under a density estimation curve. This article provides an overview of density estimation and computes an empirical cumulative density function.

Rick Wicklin 0
Overlaying two histograms in SAS

A reader commented to me that he wants to use the HISTOGRAM statement of the SGPLOT procedure to overlay two histograms on a single plot. He could do it, but unfortunately SAS was choosing a large bin width for one of the variables and a small bin width for the

Rick Wicklin 0
Pre-allocate arrays to improve efficiency

Recently Charlie Huang showed how to use the SAS/IML language to compute an exponentially weighted moving average of some financial data. In the commentary to his analysis, he said: I found that if a matrix or a vector is declared with specified size before the computation step, the program’s efficiency

Rick Wicklin 0
A statistical analysis of coupons

Each Sunday, my local paper has a starburst image on the front page that proclaims "Up to $169 in Coupons!" (The value changes from week to week.) One day I looked at the image and thought, "Does the paper hire someone to count the coupons? Is this claim a good

Learn SAS
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SAS Press to debut new statistical titles at JSM 2011

The 2011 Joint Statistical Meetings (JSM) will be from July 31-August 3 in Miami Beach. Look for acquisitions editor and SAS Press conference mega-maven Shelley Sessoms at the SAS Publishing booth (#504). Shelley can talk with you about: New and forthcoming statistics-related books from SAS Press, including Statistical Analysis for

Rick Wicklin 0
Enumerating levels of a classification variable

A colleague asked, "How can I enumerate the levels of a categorical classification variable in SAS/IML software?" The variable was a character variable with n observations, but he wanted the following: A "look-up table" that contains the k (unique) levels of the variable. A vector with n elements that contains

Chris Hemedinger 0
Moved again. Did you blink and miss it?

Sometime very recently, probably while you weren't looking, I changed jobs at SAS (yes, again). This time it's a bigger change for me, because I'm no longer part of the SAS R&D organization, where I've worked for nearly 14 years. Instead, I'm part of the team known internally as Professional

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