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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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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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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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Analytics | Learn SAS

Rick WicklinJuly 17, 2023 0

Standardize regression coefficients for models that include categorical variables

A previous article discusses standardized coefficients in linear regression models and shows how to compute standardized regression coefficients in SAS by using the STB option on the MODEL statement in PROC REG. It also discusses how to interpret a standardized regression coefficient. Recently, a SAS user wanted to know how

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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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Analytics | Learn SAS

Rick WicklinJune 26, 2023 0

Compute the geometric median of a triangle

While writing an article about labeling a polygon by using the centroid, I almost made a false claim about the centroid. I almost claimed that that the centroid is the point in a polygon that minimizes the sum of the distances to the vertices. It is not. The point that

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Analytics | Learn SAS

Rick WicklinJune 21, 2023 0

Barycentric coordinates for a triangle

A colleague asked how to compute the barycentric coordinates of a point inside a triangle. Given a triangle in the plane with vertices p1, p2, and p3, every point in the triangle can be represented as a convex combination of the vertices: c1*p1 + c2*p2 + c3*p3, where c1,c2,c3 ≥

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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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Analytics | Learn SAS

Rick WicklinJune 7, 2023 0

Visualize the Spearman rank correlation

A previous article explains the Spearman rank correlation, which is a robust cousin to the more familiar Pearson correlation. I've also discussed why you might want to use rank correlation, and how to interpret the strength of a rank correlation. This article gives a short example that helps you to

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Learn SAS

Rick WicklinJune 5, 2023 0

Moire patterns: Or why you shouldn't wear a striped shirt on a video

Since the COVID-19 pandemic began, video presentations and webcasts have become a regular routine for many of us. On days that I will be using my webcam, I wear a solid-color shirt. If I don't plan to be on camera, I can wear a pinstripe Oxford shirt. Why the difference?

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Data Visualization | Learn SAS

Rick WicklinMay 30, 2023 0

How to use a log-scale on a histogram

Real-world data often exhibits extreme skewness. It is not unusual to have data span many orders of magnitude. Classic examples are the distributions of incomes (impoverished and billionaires) and population sizes (small countries and populous nations). The readership of books and blog posts show a similar distribution, which is sometimes

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Data Visualization | Learn SAS

Rick WicklinMay 24, 2023 0

How does PROC SGPLOT position labels for polygons?

Labeling objects in graphs can be difficult. SAS has a long history of providing support for labeling markers in scatter plots and for labeling regions on a map. This article discusses how the SGPLOT procedure decides where to put a label for a polygon. It discusses the advantages and disadvantages

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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 | Analytics | Artificial Intelligence | Learn SAS | Students & Educators

Ariane Liger-Belair

Ariane Liger-BelairMay 10, 2023 0

SAS Spring Campus – le début d’une aventure folle

Finir ses études, c’est aussi la promesse exhilarante d’avoir toute sa vie devant soi et de ne pas savoir ce que la carrière a en réserve pour nous. On prend une seule décision et juste comme ça, on gère l’analytique de l’une des meilleures équipes du rugby au monde. Voilà

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Learn SAS | Machine Learning

Rick WicklinMay 10, 2023 0

How good is an AI chatbot at SAS programming?

A lot of programmers have been impressed by the ability of ChatGPT, GPT-4, and Bing Chat to write computer programs. Recently, I wrote an article that discusses an elementary programming assignment, called FizzBuzz, which is sometimes used as part of a hiring process to assess a candidate's basic knowledge of

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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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Learn SAS | SAS Events

SAS Explore call for content

Chris Hemedinger

Chris HemedingerMay 3, 2023 0

Bring your expertise to SAS Explore 2023

SAS Explore 2023 is open for your ideas and submissions! Bring your content ideas to the conference -- your experience and expertise is needed!

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Data Visualization | Learn SAS

Rick WicklinMay 1, 2023 0

Overlay a curve on a histogram in SAS

In a previous article, I showed how to overlay a density estimate on a histogram by using the Graph Template Language (GTL). However, a SAS programmer asked how to overlay a curve on a histogram when the curve is not a density estimate. In this case, the vertical axis for

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Analytics | Learn SAS

Sophia RowlandApril 26, 2023 0

Get started with ModelOps now

You can start learning about ModelOps and SAS Model Manager now. Compare the various educational resources provided by SAS according to your learning preference.

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Data Visualization | Learn SAS

Rick WicklinApril 26, 2023 0

Compatible plot types in SAS

When the SAS statistical graphics (SG) procedures were designed in the early 2000s, a goal was to create a comprehensive Graph Template Language (GTL) and leverage the GTL by using SG procedures that perform common tasks easily without having to write any GTL. This project was hugely successful, and "ODS

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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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