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Analytics | Learn SAS | Programming Tips

Rick WicklinNovember 6, 2023 0

Standard errors for maximum likelihood estimation

In several previous articles, I've shown how to use SAS to fit models to data by using maximum likelihood estimation (MLE). However, I have not previously shown how to obtain standard errors for the estimates. This article combines two previous articles to show how to obtain MLE estimates and the

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Learn SAS | Programming Tips

Rick WicklinNovember 1, 2023 0

The distribution of the sample median for normal data

A previous article shows how to use Monte Carlo simulation to approximate the sampling distribution of the sample mean and sample median. When x ~ N(0,1) are normal data, the sample mean is also normal, and there are simple formulas for the expected value and the standard error of the

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Programming Tips

Peter Styliadis

Peter StyliadisOctober 30, 2023 0

Create User Defined Functions (UDFs) for the CAS Server on SAS Viya

Welcome back to my SAS Users blog series CAS Action! - a series on fundamentals. In this post, I'll show how to create user defined functions (UDFs) for the distributed CAS server using SAS and CASL code. Once the UDF is created, you can use it on the CAS server with programming

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Learn SAS | Programming Tips

Rick WicklinOctober 30, 2023 0

The distribution of the sample median

An elementary course in statistics often includes a discussion of the sampling distribution of a statistic. The canonical example is the sampling distribution of the sample mean. For samples of size n that are drawn from a normally distribution (X ~ N(μ, σ)), the sample mean is normally distributed as

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Learn SAS | Programming Tips

Rick WicklinOctober 25, 2023 0

Quantiles of the generalized birthday problem

A previous article discusses the birthday problem and its generalizations. The classic birthday problem asks, "In a room that contains N people, what is the probability that two or more people share a birthday?" The probability is much higher than you might think. For example, in a room that contains

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Data Visualization | Programming Tips

Cindy WangOctober 23, 2023 0

How to draw a radar chart in SAS® Visual Analytics using a custom graph – Part II

In the second of a two-part series, SAS' Cindy Wang reveals how to create a custom graph template in SAS Graph Builder that can be rendered as a radar chart in SAS Visual Analytics.

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Learn SAS | Programming Tips

Rick WicklinOctober 23, 2023 0

The generalized birthday problem

The birthday-matching problem (also called the birthday paradox or simply the birthday problem), is a classic problem in probability. Simply stated, the birthday-matching problem asks, "If there are N people in a room, what is the chance that two of them have the same birthday?" The problem is sometimes called

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Analytics | Programming Tips

Junhyuk JeongOctober 20, 2023 0

컴퓨터가 사물을 보는 방법, CNN 실습 – 3편

지난 포스팅(컴퓨터가 사물을 보는 방법 1편, 2편)에서는 CNN(Convolution Neural Network)에서 사용될 수 있는 다양한 기법들과 함께 CNN의 학습이 어떤 방식으로 이루어지는지 알아보았습니다. CNN은 데이터(특히 이미지 데이터)에 합성곱, 풀링, 패딩 등의 작업을 거쳐 특징을 추출한 후 회귀 또는 분류를 수행하는 딥러닝 모델입니다. 오늘 포스팅에서는 지금까지 배운 기법들을 SAS Viya에서 구현하는 실습을

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Data Visualization | Programming Tips

Cindy WangOctober 19, 2023 0

How to draw a radar chart in SAS® Visual Analytics using a custom graph – Part I

In the first of a two-part series, SAS' Cindy Wang shows you how to create a radar chart in SAS Visual Analytics using custom graph capabilities.

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Learn SAS | Programming Tips

Rick WicklinOctober 16, 2023 0

On the evaluation of the function exp(x) - 1

Recently I wrote about numerical analysis problem: the accurate computation of log(1+x) when x is close to 0. A naive computation of log(1+x) loses accuracy if you call the LOG function, which is why the SAS language provides the built-in LOG1PX for this computation. In addition, I showed that you

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Programming Tips

Peter Styliadis

Peter StyliadisOctober 11, 2023 0

Python Integration to SAS® Viya® - Part 22 - Create User Defined Functions (UDFs)

Welcome to the continuation of my series Getting Started with Python Integration to SAS Viya. In this post I'll show how to create user defined functions (UDFs) for the distributed CAS server using the SWAT package. Once the UDF is created you can use it on the CAS server with programming

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Learn SAS | Programming Tips

Rick WicklinOctober 11, 2023 0

The LOG1PX function: Approximate functions by using Taylor series and rational functions

SAS supports a special function for the accurate evaluation of log(1+x) when x is near 0. The LOG1PX function is useful because a naive computation of log(1+x) loses accuracy when x is near 0. This article demonstrates two general approximation techniques that are often used in numerical analysis: the Taylor

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Learn SAS | Programming Tips

Rick WicklinOctober 9, 2023 0

Functions for continuous probability distributions in SAS

The documentation for Python's SciPy package provides a table that concisely summarizes functions that are associated with continuous probability distributions. This article provides a similar table for SAS functions. For more information on the CDF, PDF, quantile, and random-variate functions, see "Four essential functions for statistical programmers." SAS functions for

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Learn SAS | Programming Tips

Rick WicklinOctober 4, 2023 0

Use design matrices to analyze subgroups in SAS IML

A previous article shows ways to perform efficient BY-group processing in the SAS IML language. BY-group processing is a SAS-ism for what other languages call group processing or subgroup processing. The main idea is that the data set contains several discrete variables such as sex, race, education level, and so

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Programming Tips

Ursula PoloSeptember 29, 2023 0

Three steps to migrate OS Scheduler SAS Scheduling Jobs from SAS 9 to SAS Viya

Just coming in from an AP news source, here's your situation: At your company, you have both a SAS 9 and a SAS Viya Environment. And your problem: You want to migrate your scheduling jobs which are SAS programs from SAS 9 to a SAS Viya Environment. How can this

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Programming Tips

Rick WicklinSeptember 25, 2023 0

Define or extract the diagonals of a matrix

Many useful matrices in applied math and statistics have a banded structure. Examples include diagonal matrices, tridiagonal matrices, banded matrices, and Toeplitz matrices. An example of an unsymmetric Toeplitz matrix is shown to the right. Notice that the matrix is constant along each diagonal, including sub- and superdiagonals. Recently, I

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Data Visualization | Programming Tips

Rick WicklinSeptember 20, 2023 0

Avoid domain errors by using Taylor series

The other day I was trying to numerically integrate the function f(x) = sin(x)/x on the domain [0,∞). The graph of this function is shown to the right. In SAS, you can use the QUAD subroutine in SAS IML software to perform numerical integration. Some numerical integrators have difficulty computing

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Data Visualization | Learn SAS | Programming Tips

Rick WicklinSeptember 18, 2023 0

Use PROC SGPLOT to embed a graph inside another graph

Did you know that you can embed one graph inside another by using PROC SGPLOT in SAS? A typical example is shown to the right. The large graph shows kernel density estimates for the distribution of the Cholesterol variable among male and female patients in a heart study. The small

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Learn SAS | Programming Tips

Rick WicklinSeptember 13, 2023 0

The SG annotation macros in SAS

I don't often use the SG annotation facility in SAS for adding annotations to statistical graphics, but when I do, I enjoy the convenience of the SG annotation macros. I can never remember the details of the SG annotation commands, but I know that the SG annotation macros will create

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Learn SAS | Programming Tips

Rick WicklinSeptember 11, 2023 0

On the performance of BY-group processing in SAS IML

Many SAS procedures support a BY statement that enables you to perform an analysis for each unique value of a BY-group variable. The SAS IML language does not support a BY statement, but you can program a loop that iterates over all BY groups. You can emulate BY-group processing by

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Analytics | Learn SAS | Programming Tips

Rick WicklinSeptember 6, 2023 0

Model data from published summary statistics

There are many ways to model a set of raw data by using a continuous probability distribution. It can be challenging, however, to choose the distribution that best models the data. Are the data normal? Lognormal? Is there a theoretical reason to prefer one distribution over another? The SAS has

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Programming Tips

Yinliang WuAugust 31, 2023 0

Review garbage characters in RTF output on Unicode SAS

As SAS delivered powerful end-to-end artificial intelligence & machine learning platform SAS® Viya®, more and more SAS users plan to adopt this new platform to produce faster outcomes and invaluable insights. The significant difference between SAS Viya and SAS 9 is, UTF-8 is the default session encoding in SAS Viya,

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Learn SAS | Programming Tips

Rick WicklinAugust 30, 2023 0

Simulate the use of personal checks in the US

Does anyone write paper checks anymore? According to researchers at the Federal Reserve Bank of Atlanta (Greene, et al., 2020), the use of paper checks has declined 63% among US consumers since the year 2000. The researchers surveyed more than 3,000 consumers in 2017-2018 and discovered that only 7% of

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Advanced Analytics | Analytics | Data Management | Learn SAS | Programming Tips

Yinliang WuAugust 29, 2023 0

How to evaluate SAS expressions in PROC DS2 dynamically

Some readers read the article “how-to-evaluate-sas-expression-in-data-step-dynamically” and wonder if there is a same mechanism or functionality in DS2. As indicated in that article, SAS provides similar features in DATA step, PROC CAS and PROC Python, but some projects like ESP (Event Stream Processing) projects would store those expression definition in

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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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