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 SAS, range attribute maps enable you to specify the range of values that determine the colors used for graphical elements. There are various examples that use the GTL to define a range attribute map, but fewer examples that show how to use a range attribute map with PROC SGPLOT.
A common way to visualize the sample correlations between many numeric variables is to display a heat map that shows the Pearson correlation for each pair of variables, as shown in the image to the right. The correlation is a number in the range [-1, 1], where -1 indicated perfect
The INPUT function and PUT function in SAS are used to apply informats and formats (respectively) to data. For both functions, you must know in advance which informat or format you want to apply. For brevity, let's consider only applying a format. To use the PUT function, you must know
In SAS, the INPUT and PUT functions are powerful functions that enable you to convert data from character type to numeric type and vice versa. They work by applying SAS formats or informats to data. You cannot fully understand the INPUT and PUT functions without understanding formats and informats in
SAS software supports two kinds of procedures: interactive and non-interactive. Most SAS procedures are non-interactive. They begin with a PROC statement, include one or more additional statements, and end with a RUN statement. When SAS encounters the RUN statement, the procedure executes all statements, then exits. On the other hand,
A remarkable result in probability theory is the "three-sigma rule," which is a generic name for theorems that bound the probability that a univariate random variable will appear near the center of its distribution. This article discusses the familiar three-sigma rule for the normal distribution, a less-familiar rule for unimodal
In practice, there is no need to remember textbook formulas for the ANOVA test because all modern statistical software will perform the test for you. In SAS, the ANOVA procedure is designed to handle balanced designs (the same number of observations in each group) whereas the GLM procedure can handle
A previous article about how to display missing values in SAS prompted a comment about special missing values in ODS tables in SAS. Did you know that statistical tables in SAS include special missing values to represent certain situations in statistical analyses? This article explains how to interpret four special
In statistical tables in SAS, a dot (.) represents a numerical missing value. Although a dot is the default symbol in SAS, other languages use other symbols. The R language prints the symbol NA, which stands for "not available." The MATLAB language uses NaN ("Not a Number"). In Python, many
Modern software for statistical graphics automatically handles many details and graph defaults, such as the range of the axes and the placement of tick marks. In the days of yore, these details required tedious manual calculations. Think about what is required to place ticks on a scatter plot. On the
