This article is an excerpt from my forthcoming book Simulating Data with SAS. Not every matrix with 1 on the diagonal and off-diagonal elements in the range [–1, 1] is a valid correlation matrix. A correlation matrix has a special property known as positive semidefiniteness. All correlation matrices are positive
Michele Burlew’s new book, SAS Hash Object Programming Made Easy takes users through the newest look-up technique from SAS, one that has many still shaking their heads. “Not many DATA step programmers have used hash objects much,” Burlew says. “They seem scary because they operate a little differently from the SAS
This is a dramatic interpretation of an actual conversation I recently had with the CIO of one of North Carolina’s leading cities. We discussed his experience using data quality, data integration, business intelligence and analytics in the daily operation of the city. I may have taken some...well, a lot of
Robert Allison posted a map that shows the average commute times for major US cities, along with the proportion of the commute that is attributed to traffic jams and other congestion. The data are from a CEOs for Cities report (Driven Apart, 2010, p. 45). Robert use SAS/GRAPH software to
Ah! The joys of sets! It is easy to test whether two vectors are equal in SAS/IML software. It is only slightly more challenging to test whether two sets are equal. Recall that A and B are equal as sets if they contain the same elements. Order does not matter.
I needed to construct a string to use in the title of a scatter plot. The scatter plot showed a line, and I wanted to include the equation of the line in the plot's title. This article shows how to construct a string that contains the equation in a readable
SAS users world-wide have turned to Susan Slaughter, Lora Delwiche, and The Little SAS Book to learn SAS programming. This week's SAS tip is from their bestselling fourth edition of the book (the fifth edition is now available for preorder). Whichever version of The Little SAS Book you use, you'll benefit from the friendly
One of the often-cited side effects of moving from "Base SAS" (SAS on your PC, or Display Manager) to SAS Enterprise Guide is the loss of "X" command privileges -- that is, the ability for your SAS programs to invoke other programs via the operating system shell. We call this
Magic squares are cool. Algorithms that create magic squares are even cooler. You probably remember magic squares from your childhood: they are n x n matrices that contain the numbers 1,2,...,n2 and for which the row sum, column sum, and the sum of both diagonals are the same value. There are many
“Ohio links teacher pay to test scores” was the headline of a recent CNN School of Thought blog. Yikes! With a headline like that, teachers might start heading for the hills. I kept reading through the blog hoping that it would better explain Ohio’s policy to use student growth data
Edward Vonesh is a managing member of Vonesh Statistical Consulting, LLC, as well as a part-time employee of Northwestern University, where he supports research in his capacity as professor in the Department of Preventive Medicine. Needless to say, he knows a thing or two about generalized linear and nonlinear models.
The Perils Revisited A few posts ago I warned of the perils of forecasting benchmarks, and why they should not be used to set your forecasting performance objectives: Can you trust the data? Is measurement consistent across the respondents? Is the comparison relevant? In addition to a general suspicion about
When I studied math in school, I learned that the expression a (mod n) is always an integer between 0 and q – 1 for integer values of a and q. It's a nice convention, but SAS and many other computer languages allow the result to be negative if a (or q) is
This week's SAS tip is from A. John Bailer and his book Statistical Programming in SAS. A Fellow of the American Statistical Association, John has been using SAS for 30 years. He's also Distinguished Professor and Chair of the Department of Statistics at Miami University. To read a free chapter and user reviews
Leaving Las Vegas Prince Harry, who recently gambled away a handful of the royal family jewels during a high-stakes billiards game, doesn't have to be the only person to leave Las Vegas with some important lessons learned. You can, too, by attending the Analytics2012 conference at Caesar's Palace, October 8-9. Learnings
Regular expressions provide a powerful method to find patterns in a string of text. However, the syntax for regular expressions is somewhat cryptic and difficult to devise. This is why, by my reckoning, approximately 97% of the regular expressions used in code today were copied and pasted from somewhere else.
The other day I was using PROC SGPLOT to create a box plot and I ran a program that was similar to the following: proc sgplot data=sashelp.cars; title "Box Plot: Category = Origin"; vbox Horsepower / category=origin; run; An hour or so later I had a need for another box
Facebook has millions of users, and therefore when people share an interesting graph on Facebook it can "go viral" and millions of people might see it. Some of the graphs are obviously a bit biased - especially ones that are trying to sway your opinion one way or another on a topic
The SAS/IML language supports user-defined functions (also called modules). Many SAS/IML programmers know that you can use the RETURN function to return a value from a user-defined function. For example, the following function returns the sum of each column of matrix: proc iml; start ColSum(M); return( M[+, ] ); /*
It is common to want to extract the lower or upper triangular elements of a matrix. For example, if you have a correlation matrix, the lower triangular elements are the nontrivial correlations between variables in your data. As I've written before, you can use the VECH function to extract the
The project that I'm currently working on requires several input data tables, and those tables must have a specific schema. That is, each input table must contain columns of a specific name, type, and length in order for the rest of the system to function correctly. The schema requirements aren't
Recently, there has been lot of uproar and confusion about the Supreme Court ruling on the constitutionality of the Affordable Care Act. Many were surprised by the ruling, and others, while happy it was upheld, are concerned about the constitutional questions that arose due to the way the ruling was
I'm working on a SAS programming project with a large team. Each team member is responsible for a piece of the overall system, and the "contract" for how it all fits together is The Data. For example, I've got a piece that performs some data manipulation and produces several output
In the course of my job, I get to have a lot of conversations with authors about their books. One of the aspects of those conversations I enjoy most is learning about their areas of expertise and knowledge—that could be certain SAS software or programming techniques, particular fields of analytics,
Sometimes a small option can make a big difference. Last week I thought to myself, "I wish there were an option that prevents variable labels from appearing in a table or graph." Well, it turns out that there is! I was using PROC MEANS to display some summary statistics, and
Do you use SAS for analytics and Microsoft Excel for graphs? Why not use SAS for your graphs too?!? Then you could completely automate the entire process in one SAS program, with no manual steps! A lot of people use Excel to create their graphs because "it's what they know." What if somebody
I've seen analyses of Fisher's iris data so often that sometimes I feel like I can smell the flowers' scent. However, yesterday I stumbled upon an analysis that I hadn't seen before. The typical analysis is shown in the documentation for the CANDISC procedure in the SAS/STAT documentation. A (canonical)
When the Western Users of SAS Software gather in Long Beach, CA this September, I'll be proud to be counted among the WUSSers. (You can learn more about WUSS here; don't look here.) The WUSS organizers must have some serious clout, because the line-up of presenters reads like a "Who's
The SAS System provides users with the ability to create, store and access custom functions using the Function Compiler (FCMP) procedure. Once defined with PROC FCMP, a user-defined function can be used, or called, just like any other SAS function in the SAS System. This powerful capability gives users the
Everyone in the world has their attention turned towards the Olympics this week, so what better topic to tie in to a SAS/GRAPH blog than that?!?! I had seen a graph on the guardian website that I thought was interesting, so I decided to try to create my own (slightly different)
