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Rick WicklinSeptember 27, 2010 23

Extending IML - Defining a Function Module

The SAS/IML run-time library contains hundreds of functions and subroutines that you can call to perform statistical analysis. There are also many functions in Base SAS software that you can call from SAS/IML programs. However, one day you might need to compute some quantity for which there is no prewritten

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Rick WicklinSeptember 24, 2010 1

When is the peak of hurricane season?

Visualizing the distribution of data is a primary task of data analysis. With all the hurricane activity in the Atlantic this year, I’ve been thinking about ways to visualize the historical distribution of hurricane activity. USA Today on Friday, August 13, 2010, announced that "the heart of hurricane season is

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Rick WicklinSeptember 22, 2010 7

Efficient Sampling

Recently, SAS Global Forum announced the call for papers for the 2011 conference to be held at Caesars Palace in Las Vegas. Since the conference is in Las Vegas, I’ve been thinking a lot about games of chance: blackjack, craps, roulette, and the like. You can analyze these games by

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Rick WicklinSeptember 20, 2010 4

Five Reasons to CLOSE Your Data Sets

My mother taught me to put things away when I'm finished using them. She doesn't use a computer, but if she did, I know that she'd approve of this tip from my book: Tip: Always close your files and data sets when you are finished reading or writing them. In

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Rick WicklinSeptember 17, 2010 4

A Prime Number Sieve

Today is the birthday of Bernhard Riemann, a German mathematician who made fundamental contributions to the fields of geometry, analysis, and number theory. Riemann is definitely on my list of the greatest mathematicians of all time, and his conjecture about the distribution of prime numbers is one of the great

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Rick WicklinSeptember 15, 2010 7

Remove Observations with Missing Values

Missing values are a fact of life. Many statistical analyses, such as regression, exclude observations that contain missing values prior to forming matrix equations that are used in the analysis. This post shows how to find rows of a data matrix that contain missing values and how to remove those

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Rick WicklinSeptember 13, 2010 6

Never End PROC IML with a RUN Statement

Peter Flom reminded readers of his blog that you should always end a SAS procedure with a RUN statement. This is good rule. However, PROC IML is an exception to the rule. In PROC IML, the RUN statement is used to execute a built-in subroutine or a user-defined module. You

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Rick WicklinSeptember 10, 2010 14

LOC: The most useful function you've never heard of

A frequently performed task in data analysis is identifying all the observations in a data set that satisfy certain conditions. For example, you might want to identify all of the female patients in your study or to identify all patients whose systolic blood pressure is greater than 140 mm Hg.

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Rick WicklinSeptember 8, 2010 10

Calling Base SAS Functions from SAS/IML Programs

"How do I apply a format to a vector of values in IML? In the DATA step, I can just call the PUTN function.” This question came from a SAS customer that I met recently at a conference. My reply? Use the PUTN function, but send it a vector of

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Rick WicklinSeptember 3, 2010 8

Filling an Upper Triangular Matrix from a Vector

The R You Ready blog posed an interesting problem. Essentially, you have a vector that contains n(n+1)/2 elements, and you want to pack those elements into the upper left triangular portion of a matrix. For example, if your data are proc iml; /** vector v is given: ncol(v) = n(n+1)/2 for

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