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Strengthen your programming skills with tips and techniques from the experts

Rick WicklinFebruary 19, 2024 0

In a recent Monte Carlo project, I needed to simulate numbers on an interval by using a continuous linear probability density function (PDF). An example is shown to the right. In this example, the linear density function is decreasing on the interval, but the function could also be constant or

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Analytics | Learn SAS | Programming Tips

Rick WicklinFebruary 12, 2024 0

An exact formula for the sampling distribution of the correlation coefficient

I read a journal article in which a researcher used a formula for the probability density function (PDF) of the sample correlation coefficient. The formula was rather complicated, and presented with no citation, so I was curious to learn more. I found the distribution for the correlation coefficient in the

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Learn SAS | Programming Tips

Rick WicklinJanuary 31, 2024 1

The name of the variable that contains the largest value in each row

A SAS programmer wanted to find the name of the variable for each row that contains the largest value. This task is useful for wide data sets in which each observation has several variables that are measured on the same scale. For example, each observation in the data might represent

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Learn SAS | Programming Tips

Rick WicklinJanuary 24, 2024 1

Implement Jacobi's method in SAS

In a first course in numerical analysis, students often encounter a simple iterative method for solving a linear system of equations, known as Jacobi's method (or Jacobi's iterative method). Although Jacobi's method is not used much in practice, it is introduced because it is easy to explain, easy to implement,

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Learn SAS | Programming Tips

Rick WicklinJanuary 15, 2024 0

Simulate correlated continuous and discrete variables

Statistical software provides methods to simulate independent random variates from continuous and discrete distributions. For example, in the SAS DATA step, you can use the RAND function to simulate variates from continuous distributions (such as the normal or lognormal distributions) or from discrete distributions (such as the Bernoulli or Poisson).

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Programming Tips

Rick WicklinJanuary 10, 2024 0

Blog posts from 2023 that deserve a second look

In a previous article, I presented some of the most popular blog posts from 2023. The popular articles tend to discuss elementary topics that have broad appeal. However, I also wrote many technical articles about advanced topics. The following articles didn't make the Top 10 list, but they deserve a

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Analytics | Data Visualization | Learn SAS | Programming Tips

Rick WicklinJanuary 3, 2024 4

Top 10 posts from The DO Loop in 2023

In 2023, I wrote 90 articles for The DO Loop blog. My most popular articles were about SAS programming, data visualization, and statistics. In addition, several "general interest" articles were popular, including my article for Pi Day and an article about AI chatbots. If you missed any of these articles,

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Analytics | Learn SAS | Programming Tips

Rick WicklinDecember 4, 2023 3

Bivariate normal probability in SAS

A previous article discussed how to compute probabilities for the bivariate standard normal distribution. The standard bivariate normal distribution with correlation ρ is denoted BVN(0,ρ). For any point (x,y), you can use the PROBBNRM function in SAS to compute the probability that the random variables (X,Y) ~ BVN(0,ρ) is observed

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Analytics | Programming Tips

Rick WicklinNovember 29, 2023 1

Bivariate normal probability in SAS: Rectangular regions

This article shows how to use SAS to compute the probabilities for two correlated normal variables. Specifically, this article shows how to compute the probabilities for rectangular regions in the plane. A second article discusses the computation over infinite regions such as quadrants. If (X,Y) are random variables that are

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Analytics | Data Visualization | Programming Tips

Rick WicklinNovember 27, 2023 0

An example of finite-precision issues in a simple collinearity algorithm

The collinearity problem is to determine whether three points in the plane lie along a straight line. You can solve this problem by using middle-school algebra. An algebraic solution requires three steps. First, name the points: p, q, and r. Second, find the parametric equation for the line that passes

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