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Rick WicklinMarch 4, 2024 1

The Number-Word Game

Have you heard about the Number-Word Game? This is a simple game that has the following rules: Start with any positive integer. Write down the English word for the integer. Count the number of letters in the word. This gives a new positive integer. Go to (2). Repeat until a

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Data Visualization | Learn SAS

Rick WicklinFebruary 28, 2024 0

Using colors to visualize groups in a bar chart in SAS

I sometimes see analysts overuse colors in statistical graphics. My rule of thumb is that you do not need to use color to represent a variable that is already represented in a graph. For example, it is redundant to use a continuous color ramp to represent the lengths of bars

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Analytics | Learn SAS

Rick WicklinFebruary 26, 2024 1

On using flexible distributions to fit data

With four parameters I can fit an elephant. With five I can make his trunk wiggle. — John von Neumann Ever since the dawn of statistics, researchers have searched for the Holy Grail of statistical modeling. Namely, a flexible distribution that can model any continuous univariate data. As the quote

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Analytics | Learn SAS | Programming Tips

Rick WicklinFebruary 21, 2024 0

On using the range to estimate the variability of small samples

In statistical quality control, practitioners often estimate the variability of products that are being produced in a manufacturing plant. It is important to estimate the variability as soon as possible, which means trying to obtain an estimate from a small sample. Samples of size five or less are not uncommon

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Learn SAS | Programming Tips

Rick WicklinFebruary 19, 2024 0

The linear distribution on an interval

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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Rick WicklinFebruary 7, 2024 6

The elliptical heart

Some hearts are famous. For example, there is the "Heart of Gold" (Neil Young), the "Heart of Glass" (Blondie), and the Heart of Darkness (Joseph Conrad). But have you heard of the "Heart of Ellipses"? No? Well, in 2023, Ted Conway published an amusingly titled article, "Total Ellipse of the

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Analytics | Learn SAS

Rick WicklinFebruary 5, 2024 2

Peeling a convex hull

This article looks at a geometric method for estimating the center of a multivariate point cloud. The method is known as convex-hull peeling. In two-dimensions, you can perform convex-hull peeling in SAS 9 by using the CVEXHULL function in SAS IML software. For higher dimensions, you can use the CONVEXHULL

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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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