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Rick WicklinApril 11, 2018 4

Find the unique rows of a numeric matrix

Sometimes it is important to ensure that a matrix has unique rows. When the data are all numeric, there is an easy way to detect (and delete!) duplicate rows in a matrix. The main idea is to subtract one row from another. Start with the first row and subtract it

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Learn SAS | Programming Tips

Rick WicklinApril 2, 2018 5

The chi-square test: An example of working with rows and columns in SAS

As a general rule, when SAS programmers want to manipulate data row by row, they reach for the SAS DATA step. When the computation requires column statistics, the SQL procedure is also useful. When both row and column operations are required, the SAS/IML language is a powerful addition to a

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Analytics | Learn SAS

Rick WicklinMarch 21, 2018 2

The conjugate gradient method

I often claim that the "natural syntax" of the SAS/IML language makes it easy to implement an algorithm or statistical formula as it appears in a textbook or journal. The other day I had an opportunity to test the truth of that statement. A SAS programmer wanted to implement the

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Learn SAS | Programming Tips

Rick WicklinMarch 19, 2018 4

Compute with combinations: Maximize a function over combinations of variables

About once a month I see a question on the SAS Support Communities that involves what I like to call "computations with combinations." A typical question asks how to find k values (from a set of p values) that maximize or minimize some function, such as "I have 5 variables,

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Learn SAS | Programming Tips

Rick WicklinFebruary 26, 2018 8

How to use FIRST.variable and LAST.variable in a BY-group analysis in SAS

My article about the difference between CLASS variables and BY variables in SAS focused on SAS analytical procedures. However, the BY statement is also useful in the SAS DATA step where it is used to merge data sets and to analyze data at the group level. When you use the

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Analytics | Learn SAS

Rick WicklinFebruary 14, 2018 13

The difference between CLASS statements and BY statements in SAS

When I first learned to program in SAS, I remember being confused about the difference between CLASS statements and BY statements. A novice SAS programmer recently asked when to use one instead of the other, so this article explains the difference between the CLASS statement and BY variables in SAS

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Learn SAS | Programming Tips

Rick WicklinJanuary 29, 2018 16

How to use the new random-number generators in SAS

What is a random number generator? What are the random-number generators in SAS, and how can you use them to generate random numbers from probability distributions? In SAS 9.4M5, you can use the STREAMINIT function to select from eight random-number generators (RNGs), including five new RNGs. After choosing an RNG,

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Learn SAS | Programming Tips

Rick WicklinJanuary 10, 2018 4

10 posts from 2017 that deserve a second look

Last week I wrote about the 10 most popular articles from The DO Loop in 2017. My most popular articles tend to be about elementary statistics or SAS programming tips. Less popular are the articles about advanced statistical and programming techniques. However, these technical articles fill an important niche. Not

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Data Visualization | Learn SAS | Programming Tips

Rick WicklinJanuary 8, 2018 6

Label multiple regression lines in SAS

A SAS programmer asked how to label multiple regression lines that are overlaid on a single scatter plot. Specifically, he asked to label the curves that are produced by using the REG statement with the GROUP= option in PROC SGPLOT. He wanted the labels to be the slope and intercept

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Learn SAS | Programming Tips

Rick WicklinJanuary 3, 2018 3

The top 10 posts from The DO Loop in 2017

I wrote more than 100 posts for The DO Loop blog in 2017. The most popular articles were about SAS programming tips, statistical data analysis, and simulation and bootstrap methods. Here are the most popular articles from 2017 in each category. General SAS programming techniques INTCK and INTNX: Do you

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