The DO Loop
Statistical programming in SAS with an emphasis on SAS/IML programs
SAS has several procedures that can fit a probability distribution to data, plot a histogram, and overlay one or more density estimates: PROC UNIVARIATE in Base SAS enables you to overlay parametric density curves from about 20 common continuous probability distributions, such as normal, lognormal, and gamma. It also enables
The power method is a well-known iterative scheme to approximate the largest eigenvalue (in absolute value) of a symmetric matrix. It is useful in practice when you need only the largest eigenvalue and eigenvector of a large matrix. The method requires only matrix-vector multiplication and vector scaling. There is a
When I encounter a new function, I usually graph it to gain intuition about how the function transforms its inputs. Recently, I needed to use the Rayleigh quotient function, which is connected to the estimation of eigenvalues and eigenvectors for symmetric matrices. It has been several years since I last
The new school year had barely started when I got a call from a friend who is an elementary school principal. She told me that every morning she announces the names of students who are celebrating a birthday. "One student noticed that we've already had two days on which no
In probability and statistics, special numbers are used to compute probabilities by counting the number of ways certain events can occur. The most famous are combinations and permutations. Both are used to count the ways to arrange or select items from a set. If a set contains n elements: A
I've often wondered about the logic that the SGPLOT procedure in SAS uses to determine whether a set of graphical overlays will receive identical attributes or different attributes. (Recall that color, size, line style, and marker symbol are all examples of attributes.) I know that when you plot grouped data