The DO Loop

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Rick WicklinMay 29, 2024 5

Sometimes labels for variables get "dropped" during data preparation and cleaning. One example is when data are transposed from "wide form" to "long form." For example, suppose a data set has three variables, X, Y, and Z, each with labels. If you transpose the data to long form, the new

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Data Visualization | Programming Tips

Rick WicklinMay 22, 2024 0

Create filled density plots in SAS

A SAS programmer wanted to visualize density estimate for some univariate data. The data had several groups, so he wanted to create a panel of density estimate, which you can easily do by using PROC SGPANEL in SAS. However, the programmer's boss wanted to see filled density estimates, such as

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Learn SAS | Programming Tips

Rick WicklinMay 15, 2024 2

Rank, order, and sorting

A SAS programmer was trying to implement an algorithm in PROC IML in SAS based on some R code he had seen on the internet. The R code used the rank() and order() functions. This led the programmer to ask, "What is the different between the rank and the order?

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Analytics | Programming Tips

Rick WicklinMay 13, 2024 2

The distribution of p-values under the null hypothesis

A SAS statistical programmer recently asked a theoretical question about statistics. "I've read that 'p-values are uniformly distributed under the null hypothesis,'" he began, "but what does that mean in practice? Is it important?" I think data simulation is a great way to discuss the conditions for which p-values are

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Learn SAS | Programming Tips

Rick WicklinMay 8, 2024 1

Dice and the correctness of a simulation

At a recent conference in Las Vegas, a presenter simulated the sum of two dice and used it to simulate the game of craps. I write a lot of simulations, so I'd like to discuss two related topics: How to simulate the sum of two dice in SAS. This is

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Data Visualization | Learn SAS | Programming Tips

Rick WicklinMay 6, 2024 5

Visualize patterns of missing values

Years ago, I wrote an article that showed how to visualize patterns of missing data. During a recent data visualization talk, I discussed the program, which used a small number of SAS IML statements. An audience member asked whether it is possible to construct the same visualization by using only

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Analytics | Programming Tips

Rick WicklinApril 29, 2024 0

Bimodal and unimodal beta distributions

In a recent article, I graphed the PDF of a few Beta distributions that had a variety of skewness and kurtosis values. I thought that I had chosen the parameter values to represent a wide variety of Beta shapes. However, I was surprised to see that the distributions were all

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Analytics | Learn SAS | Programming Tips

Rick WicklinApril 22, 2024 1

Use the moment-ratio diagram to visualize the sampling distribution of skewness and kurtosis

The moment-ratio diagram is a tool that is useful when choosing a distribution that models a sample of univariate data. As I show in my book (Simulating Data with SAS, Wicklin, 2013), you first plot the skewness and kurtosis of the sample on the moment-ratio diagram to see what common

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Analytics | Learn SAS | Programming Tips

Rick WicklinApril 15, 2024 2

Distributions with specified skewness and kurtosis

A SAS programmer wanted to simulate samples from a family of Beta(a,b) distributions for a simulation study. (Recall that a Beta random variable is bounded with values in the range [0,1].) She wanted to choose the parameters such that the skewness and kurtosis of the distributions varied over range of

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Analytics | Learn SAS | Programming Tips

Rick WicklinApril 8, 2024 1

Improve the Federal Reserve's dot plot

A dot plot is a standard statistical graphic that displays a statistic (often a mean) and the uncertainty of the statistic for one or more groups. Statisticians and data scientists use it in the analysis of group data. In late 2023, I started noticing headlines about "dot plots" in the

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