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Rick WicklinFebruary 28, 2022 3

How to find release and licensing information in SAS Viya?

An experienced SAS programmer recently switched to SAS Viya and asked how to discover what products are available on his version of Viya. We discussed a few older SAS 9 procedures, and I showed him a new Viya-specific way to get information about his version of SAS and his licensed

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Rick WicklinFebruary 23, 2022 2

Test for a symmetric matrix

It is important to be able to detect whether a numerical matrix is symmetric. Some operations in linear algebra require symmetric matrices. Sometimes, you can use special algorithms to factor a symmetric matrix. In both cases, you need to test a matrix for symmetry. A symmetric matrix must be square.

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Learn SAS | Programming Tips

Rick WicklinFebruary 16, 2022 2

A trick to plot a time series that has missing values

A SAS programmer asked an interesting question: If data in a time series has missing values, can you plot a dashed line to indicate that the response is missing at some times? A simple way to achieve this is by overlaying two lines. The first line (the "bottom" line in

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Analytics | Programming Tips

Rick WicklinFebruary 14, 2022 16

Passing-Bablok regression in SAS

This article implements Passing-Bablok regression in SAS. Passing-Bablok regression is a one-variable regression technique that is used to compare measurements from different instruments or medical devices. The measurements of the two variables (X and Y) are both measured with errors. Consequently, you cannot use ordinary linear regression, which assumes that

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Rick WicklinFebruary 9, 2022 3

Billiards on a heart-shaped table

For some reason, SAS programmers like to express their love by writing SAS programs. Since Valentine's Day is next week, I thought I would add another SAS graphic to the collection of ways to use SAS to express your love. Last week, I showed how to use vector operation and

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Rick WicklinFebruary 7, 2022 1

Billiards on an elliptical table

I recently showed how to find the intersection between a line and a circle. While working on the problem, I was reminded of a fun mathematical game. Suppose you make a billiard table in the shape of a circle or an ellipse. What is the path for a ball at

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Analytics | Programming Tips

Rick WicklinFebruary 2, 2022 0

Implement a line search algorithm in SAS

Recently, I needed to implement a line search algorithm in SAS. The line search is illustrated by the figure at the right. You start with a point, p, in d-dimensional space and a direction vector, v. (In the figure, d=2, but in general d > 1.) The goal is to

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Analytics | Programming Tips

Rick WicklinJanuary 31, 2022 0

The ERF and ERFC functions for statisticians

Recently, a SAS programmer commented about one of my blog posts. He said that he had found an alternative answer on another website. Whereas my answer was formulated in terms of the normal cumulative distribution function (CDF), the other answer used the ERF function. This article shows the relationship between

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Rick WicklinJanuary 26, 2022 3

4 ways to find the k smallest and largest data values in SAS

Sometimes it is useful to know the extreme values in data. You might need to know the Top 5 or the Top 10 smallest data values. Or, the Top 5 or Top 10 largest data values. There are many ways to do this in SAS, but this article shows examples

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Analytics | Learn SAS | Programming Tips

Rick WicklinJanuary 24, 2022 0

Estimate percentiles in SAS Viya

How can you estimate percentiles in SAS Viya? This article shows how to call the percentile action from PROC CAS to estimate percentiles of variables in a CAS data table. Percentiles and quantiles are essentially the same (the pth quantile is the 100*pth percentile for p in [0, 1]), so

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