I love GitHub for version control and collaboration, though I'm no master of it. And the tools for integrating git and GitHub with RStudio are just amazing boons to productivity. Unfortunately, my University-supplied computer does not play well with GitHub. Various directories are locked down, and I can't push or ...

I've been working on a Shiny app and wanted to display some math equations. It's possible to use LaTeX to show math using MathJax, as shown in this example from the makers of Shiny. However, by default, MathJax does not allow in-line equations, because the dollar sign is used so ...

In the US, it's typical to borrow a fairly substantial portion of the cost of a new house from a bank. The cost of these loans, the mortgage rate, varies over time depending on what the financial wizards see in their crystal balls. What this means over time is that ...

In 2012, we presented a post showing how to run RStudio in the cloud on an Amazon server. There were 7 steps, including one with 7 sub-steps, one of which had 6 sub-sub-steps. It was still pretty easy, for what it was-- an effectively free computer i...

Data with repeated measures often come to us in the "wide" format, as shown below for the HELP data set we use in our book. Here we show just an ID, the CESD depression measure from four follow-up assessments, plus the baseline CESD. Obs ID CESD1 CESD2 CESD3 CESD4 CESD 1 1 7 . 8 5 49 2 2 11 . . . 30 3 3 14 . . 49 39 4 4 44 . . 20 15 5 5 26 27 15 28 39... ...

As we discuss in section 6.1.4 of the second edition, R and SAS handle categorical variables and their parameterization in models quite differently. SAS treats them on a procedure-by-procedure basis, which leads to some odd differences in capabilities and default parameterizations. For example, in the logistic procedure, the default is effect ...

In our last entry, we demonstrated how to simulate data from a logistic regression with an interaction between a dichotomous and a continuous covariate. In this entry we show how to use the simulation to estimate the power to detect that interaction. ...

We're both users of multiple imputation for missing data. We believe it is the most practical principled method for incorporating the most information into data analysis. In fact, one of our more successful collaborations is a review of software for ...

Rick Wicklin showed how to make a Hilbert matrix in SAS/IML. Rick has a nice discussion of these matrices and why they might be interesting; the value of H_{r,c} is 1/(r+c-1). We show how to make this matrix in the data step and in R. We ...

One common violation of the assumptions needed for linear regression is heterscedasticity by group membership. Both SAS and R can easily accommodate this setting. Our data today comes from a real example of vitamin D supplementation of milk. Four sup...

This week I had to block-randomize some units. This is ordinarily the sort of thing I would do in SAS, just because it would be faster for me. But I had already started work on the project R, using knitr/LaTeX to make a PDF, so it made sense to ...

Hello, folks! I'm pleased to report that Nick and I have turned in the manuscript for the second edition of SAS and R: Data Management, Statistical Analysis, and Graphics. It should be available this summer. New material includes some of our more po...