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Strengthen your programming skills with tips and techniques from the experts

Analytics | Data Visualization | Programming Tips

Rick WicklinAugust 28, 2023 0

Generate random uniform points in an ellipse

I have previously written about how to efficiently generate points uniformly at random inside a sphere (often called a ball by mathematicians). The method uses a mathematical fact from multivariate statistics: If X is drawn from the uncorrelated multivariate normal distribution in dimensiond, then S = r*X / ||X|| has

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Programming Tips

Peter Styliadis

Peter StyliadisAugust 25, 2023 0

Python Integration to SAS® Viya® - Part 21 - Impute Missing Values

Welcome to the continuation of my series Getting Started with Python Integration to SAS Viya. In this post I'll show how to impute missing values in a distributed CAS table using the fillna method from the Pandas API in the SWAT package and the impute CAS action. Load and prepare data

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Advanced Analytics | Programming Tips

Noah HanAugust 18, 2023 0

결측 대체 함수, ‘COALESCE, COALESCEC’ 들여다보기

실무에서 데이터를 다루다 보면 필연적으로 결측 데이터를 만나게 됩니다. 핑계 없는 무덤이 없다는 속담이 있듯, 데이터가 결측인 이유도 정말 다양합니다. 특별한 경우에만 값이 있는 경우, 서버 장애로 관측되지 않은 경우, 응답자가 응답을 거부하는 경우, 데이터 구조가 바뀌면서 새로운 컬럼이 추가된 경우 등등 너무 다양하죠? 오늘 포스팅에서는 이와 같은 결측치를 처리하는

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Learn SAS | Programming Tips

Rick WicklinAugust 16, 2023 0

Add Unicode symbols and format text labels in SAS

It has been more than a decade since SAS 9.3 changed the default ODS destination from the old LISTING destination to more modern destinations such as HTML. One of the advantages of modern output destinations is support for Unicode symbols, superscripts, subscripts, and for formatting text by using boldface, italics,

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Analytics | Learn SAS | Programming Tips

Rick WicklinAugust 14, 2023 0

Bootstrap confidence intervals for the predicted mean in a regression model

In ordinary least squares regression, there is an explicit formula for the confidence limit of the predicted mean. That is, for any observed value of the explanatory variables, you can create a 95% confidence interval (CI) for the predicted response. This formula assumes that the model is correctly specified and

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Programming Tips

Peter Styliadis

Peter StyliadisAugust 10, 2023 0

Python Integration to SAS® Viya® - Part 20 - Remove Duplicate Rows

Welcome to the continuation of my series Getting Started with Python Integration to SAS Viya. In this post I'll discuss how to remove duplicate rows from a distributed CAS table using the both the Pandas API in the SWAT package and the native CAS action. The Pandas API drop_duplicates method was

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Learn SAS | Programming Tips

Rick WicklinAugust 9, 2023 0

Plot confidence intervals for a regression model in SAS

A SAS programmer wanted to use PROC SGPLOT in SAS to visualize a regression model. The programmer wanted to visualize confidence limits for the predicted mean at certain values of the explanatory variable. This article shows two options for adding confidence limits to a scatter plot. You can use a

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Learn SAS | Programming Tips

Rick WicklinAugust 7, 2023 0

Construct an envelope function for the acceptance-rejection method

The acceptance-rejection method (sometimes called rejection sampling) is a method that enables you to generate a random sample from an arbitrary distribution by using only the probability density function (PDF). This is in contrast to the inverse CDF method, which uses the cumulative distribution function (CDF) to generate a random

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Analytics | Learn SAS | Programming Tips

Noah HanJuly 31, 2023 0

SoDA 서비스 가입하기

SoDA를 이용해 쉽게 배우는 데이터 과학 #2 지난 포스팅에서는 SoDA(SAS Ondemand for Academics)의 장점과 필요성을 중심으로 SoDA가 어떤 제품인지 소개해 드렸습니다. 이번 포스팅에서는 ‘서비스 가입 방법’을 알아보겠습니다. 먼저 SoDA가 서비스 되는 브라우저 환경을 알아보고, 이어서 서비스 가입의 각 단계를 살펴보겠습니다. * 편집자 주 : 이번 글은 SAS코리아 컨설팅 본부 한노아

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Learn SAS | Programming Tips

Rick WicklinJuly 31, 2023 0

Create a probability distribution from almost any positive function

There are dozens of common probability distributions for a continuous univariate random variable. Familiar examples include the normal, exponential, uniform, gamma, and beta distributions. Where did these distributions come from? Well, some mathematician needed a model for a stochastic process and wrote down the equation for the distribution, typically by

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Programming Tips

Rick WicklinJuly 26, 2023 0

The trace of a matrix of crossproducts

Let X be any rectangular matrix. What is the trace of the crossproducts matrix, X'*X? Interestingly, you do not need to form the crossproducts matrix to compute the answer! It turns out that tr(X'*X) equals the sum of the squared elements of X. Theorem: For any matrix, X, the trace

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Analytics | Programming Tips

Rick WicklinJuly 24, 2023 0

Modifications of the Wilcoxon signed rank test and exact p-values

In a previous article, I discussed the Wilcoxon signed rank test, which is a nonparametric test for the location of the median. The Wikipedia article about the signed rank test mentions a variation of the test due to Pratt (1959). Whereas the standard Wilcoxon test excludes values that equal μ0

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Analytics | Learn SAS | Programming Tips

Rick WicklinJuly 19, 2023 0

On the computation of the Wilcoxon signed rank statistic

Wilcoxon's signed rank test is a popular nonparametric alternative to a paired t test. In a paired t test, you analyze measurements for subjects before and after some treatment or intervention. You analyze the difference in the measurements for each subject, and test whether the mean difference is significantly different

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Learn SAS | Programming Tips

Rick WicklinJuly 10, 2023 0

Simulate from a Markov model

A previous article shows an example of a Markov chain model and computes the probability that the system ends up in a terminal state (called an absorbing state). As explained previously, you can often compute exact probabilities for questions about Markov chains. Nevertheless, it can be useful to know how

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Learn SAS | Programming Tips

Rick WicklinJuly 5, 2023 0

The probability of reaching a terminal state in a Markov chain

A previous article shows how to model the probabilities in a discrete-time Markov chain by using a Markov transition matrix. A Markov chain is a discrete-time stochastic process for which the current state of the system determines the probability of the next state. In this process, the probabilities for transitioning

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Analytics | Learn SAS | Programming Tips

Rick WicklinJune 28, 2023 0

Compute the geometric median in SAS

Given a set of N points in k-dimensional space, can you find the location that minimizes the sum of the distances to the points? The location that minimizes the distances is called the geometric median of the points. For univariate data, the "points" are merely a set of numbers $${p_1,

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Learn SAS | Programming Tips

Rick WicklinJune 19, 2023 0

Use built-in ODS templates to display SAS tables

Part of the power of the SAS ODS system is the ability to visualize data by using ODS templates. An ODS template describes how to render data as a table or as a graph. A lot of papers and documentation have been written about how to define a custom template

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Learn SAS | Programming Tips

Rick WicklinJune 14, 2023 0

Eigenvalues of a tridiagonal Toeplitz matrix

While writing an article about Toeplitz matrices, I saw an interesting fact about the eigenvalues of tridiagonal Toeplitz matrices on Nick Higham's blog. Recall that a Toeplitz matrix is a banded matrix that is constant along each diagonal. A tridiagonal Toeplitz matrix is zero except for the main diagonal, the

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Learn SAS | Programming Tips

Rick WicklinJune 12, 2023 0

How to construct an unsymmetric Toeplitz matrix

A Toeplitz matrix is a banded matrix. You can construct it by specifying the parameters that are constant along each diagonal, including sub- and super-diagonals. For a square N x N matrix, there is one main diagonal, N-1 sub-diagonals, and N-1 super-diagonals, for a total of 2N-1 parameters. In statistics and applied

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Analytics | Learn SAS | Programming Tips

Noah HanJune 7, 2023 0

SoDA로 데이터 과학 시작하기

SoDA를 이용해 쉽게 배우는 데이터 과학 #1 SoDA(SAS OnDemand for Academics)는 SAS가 무료로 제공하는 교육용 데이터 분석 소프트웨어 프로그램입니다. 앞으로 4회에 걸쳐 'SoDA 를 이용해 쉽게 배우는 데이터 과학'을 자세히 소개해 드리도록 하겠습니다. SoDA란? SoDA (SAS OnDemand for Academics; SoDA)는 데이터 과학을 처음 배우는 입문자들에게 SAS를 무료로 배울 수 있도록

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Programming Tips

Leonid BatkhanMay 30, 2023 0

Embedding any code anywhere into SAS programs

SAS expert Leonid Batkhan presents the %embed macro function as a way to embed both “foreign” and SAS native code from a file into a SAS program, preventing clutter in your code.

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Programming Tips

Peter Styliadis

Peter StyliadisMay 30, 2023 0

Getting Started with Python Integration to SAS® Viya® - Part 19 - Load Multiple CSV Files

Welcome to the continuation of my series Getting Started with Python Integration to SAS Viya. In this post I'll discuss how to load multiple CSV files into memory as a single table using the loadTable action. Load and prepare data on the CAS server To start, we need to create multiple

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Learn SAS | Programming Tips

Rick WicklinMay 22, 2023 0

Rank character variables in SAS

SAS supports many ways to compute the rank of a numeric variable and to handle tied values. However, sometimes I need to rank the values in a character categorical variable. For example, the values {"Male", "Female", "Male"} have ranks {2, 1, 2} because, in alphabetical order, "Female" is the first-ranked

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Advanced Analytics | Data Visualization | Programming Tips

Rick WicklinMay 17, 2023 0

Compute the silhouette statistic in SAS

A previous article defines the silhouette statistic (Rousseeuw, 1987) and shows how to use it to identify observations in a cluster analysis that are potentially misclassified. The article provides many graphs, including the silhouette plot, which is a bar chart or histogram that displays the distribution of the silhouette statistic

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Learn SAS | Programming Tips

Rick WicklinMay 8, 2023 0

An interview question for SAS programmers

Recently, I learned about an elementary programming assignment called the FizzBuzz program. Some companies use this assignment for the first round of interviews with potential programmers. A competent programmer can write FizzBuzz in 5-10 minutes, which leaves plenty of time to discuss other topics. If an applicant can't complete the

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Programming Tips

George BeeversMay 4, 2023 0

Debunking the myth that SAS code doesn't work in Viya: One billion lines later and the results are...

The SAS 9 Content Assessment is a collection of applications that are designed to help users understand the various characteristics of their deployment. SAS Content Assessment delivers information that is critical to helping you to upgrade to the latest version of SAS (Viya).

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Analytics | Programming Tips

Rick WicklinMay 3, 2023 0

The exponential of a matrix

In SAS, you can approximate the exponential of a matrix by using the EXPMATRIX function in SAS IML software. This article discusses the exponential of a matrix: what it is, how to compute it, why it is useful, and why you should think of it as a linear map that

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Learn SAS | Programming Tips

Rick WicklinApril 24, 2023 0

Venn diagrams that illustrate relationships between sets

A previous article discusses how to compute the union, intersection, and other subsets of a pair of sets. In that article, I displayed a simple Venn diagram (reproduced to the right) that illustrates the intersection and difference between two sets. The diagram uses a red disk for one set, a

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Learn SAS | Programming Tips

Lee Ann DietzApril 21, 2023 0

Public Health Transformation: Ways to use SAS Viya

We demonstrate a few common and essential public health functions using SAS Viya. Our goal is to show the art of the possible within the realm of accessibility.

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Programming Tips

Peter Styliadis

Peter StyliadisApril 19, 2023 0

Getting Started with Python Integration to SAS® Viya® - Part 18 - Update rows in a table

Welcome to the continuation of my series Getting Started with Python Integration to SAS Viya. In this post I'll discuss how to update rows in a distributed CAS table. Load and prepare data in the CAS server I created a script to load and prepare data in the CAS server. This

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