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.
In this International Year of Statistics, I'd like to describe the major role of statistics in public health advances. In our modern society, it is sometimes difficult to recall the huge advances in health and medicine in the 20th century. To name a few: penicillin was discovered in 1928, risk
A SAS customer asks: How do I use SAS to generate multiple samples of size N from a multivariate normal distribution? Suppose that you want to simulate k samples (each with N observations) from a multivariate normal distribution with a given mean vector and covariance matrix. Because all of the
ODS statements are global SAS statements. As such, you can put them anywhere in your SAS program. For maximum readability, many SAS programmers agree that most ODS statements should appear outside procedures in "open" SAS code. For example, most programmers agree that the following statements should appear outside of procedures:
I was recently asked how to compute the difference between two density estimates in SAS. The person who asked the question sent me a link to a paper from The Review of Economics and Statistics that contains several examples of this technique (for example, see Figure 3 on p. 16
Did you know that your ODS style might result in changing the color ramp for contour plots and heat maps? For example, the default style in SAS 9.3 is HTMLBlue. Let's create a contour plot in the HTML destination by running an example adapted from the documentation for the RSREG
In statistics, distances between observations are used to form clusters, to identify outliers, and to estimate distributions. Distances are used in spatial statistics and in other application areas. There are many ways to define the distance between observations. I have previously written an article that explains Mahalanobis distance, which is
It is easy to use the SGPLOT procedure in SAS to plot the graph of a well-behaved continuous function: just create a data set of the (x,y) values on some domain and use the SERIES statement to connect the points. However, to plot the graph of a discontinuous function correctly
Someone recently asked a question on the SAS Support Communities about estimating parameters in ridge regression. I answered the question by pointing to a matrix formula in the SAS documentation. One of the advantages of the SAS/IML language is that you can implement matrix formulas in a natural way. The
One purpose of this International Year of Statistics is to spread the word that the field of statistics benefits society. As part of the International Year, many organizations, including SAS and the American Statistical Association (ASA), are turning to history to illustrate how statistics is vital to the health and
Argh! I've just spilled coffee on output that shows the least squares coefficients for a regression model that I was investigating. Now the parameter estimate for the intercept is completely obscured, although I can still see the parameter estimates for the coefficients of the continuous explanatory variable. What can I
