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Programming Tips

Rick WicklinAugust 26, 2019 9

Conditionally append observations to a SAS data set

Most SAS programmers know how to use PROC APPEND or the SET statement in DATA step to unconditionally append new observations to an existing data set. However, sometimes you need to scan the data to determine whether or not to append observations. In this situation, many SAS programmers choose one

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Programming Tips

Rick WicklinAugust 21, 2019 0

Two tips for optimizing a function that has a restricted domain

An important application of nonlinear optimization is finding parameters of a model that fit data. For some models, the parameters are constrained by the data. A canonical example is the maximum likelihood estimation of a so-called "threshold parameter" for the three-parameter lognormal distribution. For this distribution, the objective function is

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Learn SAS | Programming Tips

Rick WicklinAugust 19, 2019 2

Timing performance in SAS/IML: Built-in functions versus Base SAS functions

One of my friends likes to remind me that "there is no such thing as a free lunch," which he abbreviates by "TINSTAAFL" (or TANSTAAFL). The TINSTAAFL principle applies to computer programming because you often end up paying a cost (in performance) when you call a convenience function that simplifies

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Learn SAS | Programming Tips

Rick WicklinAugust 14, 2019 6

Short-circuit evaluation and logical ligatures in SAS

Many programmers are familiar with "short-circuit" evaluation in an IF-THEN statement. Short circuit means that a program does not evaluate the remainder of a logical expression if the value of the expression is already logically determined. The SAS DATA step supports short-circuiting for simple logical expressions in IF-THEN statements and

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Learn SAS | Programming Tips

Rick WicklinAugust 7, 2019 3

The essential guide to binning in SAS

Do you want to bin a numeric variable into a small number of discrete groups? This article compiles a dozen resources and examples related to binning a continuous variable. The examples show both equal-width binning and quantile binning. In addition to standard one-dimensional techniques, this article also discusses various techniques

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Learn SAS | Machine Learning | Programming Tips

Rick WicklinAugust 5, 2019 8

How to use PROC HPBIN to bin numerical variables

Binning transforms a continuous numerical variable into a discrete variable with a small number of values. When you bin univariate data, you define cut point that define discrete groups. I've previously shown how to use PROC FORMAT in SAS to bin numerical variables and give each group a meaningful name

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Learn SAS | Programming Tips

Rick WicklinJuly 31, 2019 3

Use numeric values for column headers when printing a matrix

Sometimes a little thing can make a big difference. I am enjoying a new enhancement of SAS/IML 15.1, which enables you to use a numeric vector as the column header or row header when you print a SAS/IML matrix. Prior to SAS/IML 15.1, you had to use the CHAR or

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Learn SAS | Programming Tips

Rick WicklinJuly 29, 2019 2

Vectorize the computation of the Mandelbrot set in a matrix language

When my colleague, Robert Allison, blogged about visualizing the Mandelbrot set, I was reminded of a story from the 1980s, which was the height of the fractal craze. A research group in computational mathematics had been awarded a multimillion-dollar grant to purchase a supercomputer. When the supercomputer arrived and got

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Learn SAS | Programming Tips

Rick WicklinJuly 24, 2019 4

Implement the Gumbel distribution in SAS

SAS supports more than 25 common probability distributions for the PDF, CDF, QUANTILE, and RAND functions. Of course, there are infinitely many distributions, so not every possible distribution is supported. If you need a less-common distribution, I've shown how to extend the functionality of Base SAS (by using PROC FCMP)

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Programming Tips

Rick WicklinJuly 17, 2019 2

Write numeric and character matrices to a data set from SAS/IML

In the SAS/IML language, a matrix contains data of one type: numeric or character. If you want to create a SAS data set that contains mixed-type data (numeric and character), SAS/IML 15.1 provides support to write multiple matrices to a data set by using a single statement. Specifically, the CREATE

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