The DO Loop

Programming Tips

Strengthen your programming skills with tips and techniques from the experts

Rick WicklinSeptember 25, 2019 2

One of the strengths of the SAS/IML language is its flexibility. Recently, a SAS programmer asked how to generalize a program in a previous article. The original program solved one optimization problem. The reader said that she wants to solve this type of problem 300 times, each time using a

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Analytics | Data Visualization | Programming Tips

Rick WicklinSeptember 16, 2019 0

The Hull moving average: Implement a custom time series smoother in SAS

A moving average is a statistical technique that is used to smooth a time series. My colleague, Cindy Wang, wrote an article about the Hull moving average (HMA), which is a time series smoother that is sometimes used as a technical indicator by stock market traders. Cindy showed how to

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Analytics | Data Visualization | Programming Tips

Rick WicklinSeptember 5, 2019 4

Use cosine similarity to make recommendations

When you order an item online, the website often recommends other items based on your purchase. In fact, these kinds of "recommendation engines" contributed to the early success of companies like Amazon and Netflix. SAS uses a recommender engine to suggest articles on the SAS Support Communities. Although recommender engines

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Analytics | Data Visualization | Programming Tips

Rick WicklinSeptember 3, 2019 8

Cosine similarity of vectors

An important application of the dot product (inner product) of two vectors is to determine the angle between the vectors. If u and v are two vectors, then cos(θ) = (u ⋅ v) / (|u| |v|) You could apply the inverse cosine function if you wanted to find θ in

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Data Visualization | Programming Tips

Rick WicklinAugust 28, 2019 2

Annotate features of a schematic box plot in SGPLOT

A SAS programmer asked an intriguing question on the SAS Support Communities: Can you use SAS to create a graph that shows how the elements in a box-and-whiskers plot relate to the data? The SAS documentation has several examples that explain how to read a box plot. One of the

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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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