Analytics | Learn SAS | Programming Tips

Rick WicklinMay 2, 2022 0

Simulate the null distribution for a hypothesis test

Recently, I wrote about Bartlett's test for sphericity. The purpose of this hypothesis test is to determine whether the variables in the data are uncorrelated. It works by testing whether the sample correlation matrix is close to the identity matrix. Often statistics textbooks or articles include a statement such as

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Learn SAS | Programming Tips

Rick WicklinApril 25, 2022 0

Two perspectives on numerical integration

To a numerical analyst, numerical integration has two meanings. Numerical integration often means solving a definite integral such as $$int_{a}^b f(s) , ds$$. Numerical integration is also called quadrature because it computes areas. The other meaning applies to solving ordinary differential equations (ODEs). My article about new methods for solving

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Data Visualization | Learn SAS | Programming Tips

Rick WicklinApril 20, 2022 0

Use a heat map to visualize an ordinal response in longitudinal data

Recently, I showed how to use a heat map to visualize measurements over time for a set of patients in a longitudinal study. The visualization is sometimes called a lasagna plot because it presents an alternative to the usual spaghetti plot. A reader asked whether a similar visualization can be

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Programming Tips

Peter StyliadisApril 20, 2022 0

CAS-Action! Create Columns in CAS Tables - Part 2

Welcome back to my SAS Users blog series CAS Action! - a series on fundamentals. This post builds upon CAS-Action! Create Columns in CAS Tables - Part 1 by showing how to add formats and modify the length of computed columns. I'll start by building off the following code where I

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Programming Tips

Martin MinceyApril 18, 2022 0

Getting started using SASPy® and the SAS® kernel for Jupyter Notebook

SASPy and the SAS kernel for Jupyter Notebook enable you to connect to SAS® 9.4 and the SAS® Viya® compute server from your client machine. You can then interact with SAS and SAS Viya via Python. If you are not familiar with SASPy and the SAS kernel, this article provides an introduction.

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Programming Tips

Peter StyliadisApril 13, 2022 0

CAS-Action! Create Columns in CAS Tables - Part 1

Welcome back to my SAS Users blog series CAS Action! - a series on fundamentals. I've broken the series into logical, consumable parts. If you'd like to start by learning a little more about what CAS Actions are, please see CAS Actions and Action Sets - a brief intro. Or if you'd

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Programming Tips

Peter StyliadisApril 11, 2022 0

CAS-Action! Filtering Rows in CAS Tables

Welcome back to my SAS Users blog series CAS Action! - a series on fundamentals. I've broken the series into logical, consumable parts. If you'd like to start by learning a little more about what CAS Actions are, please see CAS Actions and Action Sets - a brief intro. Or if you'd

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Analytics | Programming Tips

Rick WicklinApril 6, 2022 0

A differential equation for quantiles of a distribution

The graph to the right is the quantile function for the standard normal distribution, which is sometimes called the probit function. Given any probability, p, the quantile function gives the value, x, such that the area under the normal density curve to the left of x is exactly p. This

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Analytics | Data Visualization | Programming Tips

Nicole BallApril 5, 2022 0

The AggregateTable operator… It’s the bee’s knees!

Have you ever heard something referred to as the bee’s knees? Most likely the person uttering that expression meant that it was truly amazing and extraordinary. Maybe you stopped and pondered the origin of the phrase. Well wonder no more! In the 1920s in the United States, people were obsessed

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Data Visualization | Programming Tips

Rick WicklinApril 4, 2022 0

Modify an ODS style to change the missing-value color

Oh, no! Your boss just told you to change the way that SAS displays certain features in graphs, such as missing values. But you have a library of hundreds of SAS programs! Do you need to modify all of your previous programs? Fortunately, the answer is no. SAS provides ODS

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Data Visualization | Learn SAS | Programming Tips

Rick WicklinMarch 30, 2022 0

Change the missing-value color by using a range attribute map

In an article about how to visualize missing data in a heat map, I noted that the SAS SG procedures (such as PROC SGPLOT) use the GraphMissing style element to color a bar or tile that represents a missing value. In the HTMLBlue ODS style, the color for missing values

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Learn SAS | Programming Tips

Rick WicklinMarch 28, 2022 0

Use a heat map to visualize missing values in longitudinal data

Longitudinal data are measurements for a set of subjects at multiple points in time. Also called "panel data" or "repeated measures data," this kind of data is common in clinical trials in which patients are tracked over time. Recently, a SAS programmer asked how to visualize missing values in a

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Learn SAS | Programming Tips

Rick WicklinMarch 23, 2022 0

Compute properties of discrete probability distributions

This article shows how to compute properties of a discrete probability distribution from basic definitions. You can use the definitions to compute the mean, variance, and median of a discrete probability distribution when there is no simple formula for those quantities. This article is motivated by two computational questions about

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Programming Tips

Ron CodyMarch 22, 2022 0

Fun with Ciphers (Part 2)

In my previous blog, you saw how to create a Beale cipher. In this blog, you will see a program that can decode a Beale cipher. As a reminder, here is a list of numbers that you can use as a substitute for a letter when creating your cipher. Now,

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Learn SAS | Programming Tips

Rick WicklinMarch 21, 2022 0

Five constants every statistical programmer should know

Statistical programmers need to access numerical constants that help us to write robust and accurate programs. Specifically, it is necessary to know when it is safe to perform numerical operations such as raising a number to a power without exceeding the largest number that is representable in finite-precision arithmetic. This

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Programming Tips

Chris HemedingerMarch 17, 2022 0

Programming the Wordle game in SAS

One approach to creating the Wordle game in the SAS programming language. Ready to play?

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Analytics | Learn SAS | Programming Tips

Rick WicklinMarch 16, 2022 0

Least-squares optimization and the Gauss-Newton method

A previous article showed how to use SAS to compute finite-difference derivatives of smooth vector-valued multivariate functions. The article uses the NLPFDD subroutine in SAS/IML to compute the finite-difference derivatives. The article states that the third output argument of the NLPFDD subroutine "contains the matrix product J`*J, where J is

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Learn SAS | Programming Tips

Rick WicklinMarch 14, 2022 0

The pi_th roots of unity

On this Pi Day, let's explore the "πth roots of unity." (Pi Day is celebrated in the US on 3/14 to celebrate π ≈ 3.14159....) It's okay if you've never heard of the πth roots of unity. This article starts by reviewing the better-known nth roots of unity. It then

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Programming Tips | Students & Educators

Leonid BatkhanMarch 14, 2022 0

Calculating circle areas and sphere volumes without π

For Pi Day, veteran SAS user Leonid Batkhan reveals a pi paradox.

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Data Visualization | Programming Tips

Rick WicklinMarch 9, 2022 0

The Beatty sequence for pi

Did you know that you can use π to partition the positive integers into two disjoint groups? It's not hard. One group is generated by the integer portions of multiples of π. The FLOOR function gives the integer portion of a positive number, so you can write integer that are

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Analytics | Programming Tips

Rick WicklinMarch 7, 2022 0

Finite-difference derivatives of vector-valued functions

I previously showed how to use SAS to compute finite-difference derivatives for smooth scalar-valued functions of several variables. You can use the NLPFDD subroutine in SAS/IML software to approximate the gradient vector (first derivatives) and the Hessian matrix (second derivatives). The computation uses finite-difference derivatives to approximate the derivatives. The

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Analytics | Programming Tips

Rick WicklinMarch 2, 2022 0

Finite-difference derivatives in SAS

Many applications in mathematics and statistics require the numerical computation of the derivatives of smooth multivariate functions. For simple algebraic and trigonometric functions, you often can write down expressions for the first and second partial derivatives. However, for complicated functions, the formulas can get unwieldy (and some applications do not

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Learn SAS | Programming Tips

Rick WicklinFebruary 28, 2022 0

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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Learn SAS | Programming Tips

Rick WicklinFebruary 23, 2022 0

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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Programming Tips

Ron CodyFebruary 17, 2022 0

Fun with Ciphers (Part 1)

This blog serves two purposes: the main purpose is to show you some useful SAS coding techniques, and the second is to show you an interesting method of creating a Beale cipher. TJ Beale is famous in Virginia for leaving behind three ciphers, supposedly describing the location of hidden gold

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Learn SAS | Programming Tips

Leonid BatkhanFebruary 16, 2022 0

SAS open-source treasures from around the world: SASjs

Veteran SAS user Leonid Batkhan introduces you to open-source SASjs framework.

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Learn SAS | Programming Tips

Rick WicklinFebruary 16, 2022 0

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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Artificial Intelligence | Data Visualization | Programming Tips | Students & Educators

Yinliang WuFebruary 15, 2022 0

Solve the Missionaries and Cannibals Problem with SAS

The Missionaries and Cannibals Problem (MCP) is a classic river-crossing logic puzzle. With SAS, we can solve this problem, visualize the solutions with SAS NETDRAW procedure and generate steps for any MCP problems.

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Data Management | Learn SAS | Programming Tips

Bari LawhornFebruary 14, 2022 0

Where are the files that you have access to through SAS® Studio?

SAS' Bari Lawhorn shows you how to access files you've stored with SAS® Studio.

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Analytics | Programming Tips

Rick WicklinFebruary 14, 2022 0

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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