Rick Wicklin, PhD, is a distinguished researcher in computational statistics at SAS and is a principal developer of SAS/IML software. His areas of expertise include computational statistics, simulation, statistical graphics, and modern methods in statistical data analysis. Rick is author of the books Statistical Programming with SAS/IML Software and Simulating Data with SAS.
A common task in data analysis is to locate observations that satisfy multiple criteria. For example, you might want to locate all zip codes in certain counties within specified states. The SAS DATA step contains the powerful WHERE statement, which enables you to extract a subset of data that satisfy
Last week I attended SAS Global Forum 2015 in Dallas. It was packed with almost 5,000 attendees. I learned many interesting things at the conference, including the fact that you need to arrive EARLY to the statistical presentations if you want to find an empty seat! It was gratifying to
Did you know that if you have set multiple titles in SAS, that there is an easy way to remove them? For example, suppose that you've written the following statements, which call the TITLE statement to set three titles: title "A Great Big Papa Title"; title2 "A Medium-sized Mama Title";
Suppose that you compute the correlation matrix (call it R1) for a set of variables x1, x2, ..., x8. For some reason, you later want to compute the correlation matrix for the variables in a different order, maybe x2, x1, x7,..., x6. Do you need to go back to the
Sometimes different communities use the same name for different objects. To a soldier, "boots" are rugged, heavy, high-top foot coverings. To a soccer (football) player, "boots" are lightweight cleats. So it is with the term "waterfall plot." To researchers in the medical field, a "waterfall plot" is a sorted bar
A customer asked: How do we go about summing a finite series in SAS? For example, I want to compute for various integers n ≥ 3. I want to output two columns, one for the natural numbers and one for the summation of the series. Summations arise often in statistical
In clinical trials, a waterfall plot is often used to indicate how patients in the study responded to treatment. In oncology trials, the response variable might be the percent change in the size of a tumor from the individual's baseline value at the start of the trial. The percent change
Last week I was chatting with some mathematicians and I mentioned the blog post that I wrote last year on the distribution of Pythagorean triples. In my previous article, I showed that there is an algorithm that uses matrix multiplication to generate every primitive Pythagorean triple by starting with the
Today is my 600th blog post for The DO Loop. I have written about many topics that are related to statistical programming, math, statistics, simulation, numerical analysis, matrix computations, and more. The right sidebar of my blog contains a tag cloud that links to many topics. What topics do you,
A common question from statistical programmers is how to compute the rank of a matrix in SAS. Recall that the rank of a matrix is defined as the number of linearly independent columns in the matrix. (Equivalently, the number of linearly independent rows.) This article describes how to compute the
