Blog Archives

A word of warning about grep, which and the like

July 13, 2011
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A word of warning about grep, which and the like

I’ve often selected columns or rows of a data frame using grep or which, based on some property. That is inherently sound, but the trouble comes when you wish to remove rows or columns based on that grep or which call, e.g., which would remove columns with a .1 in the name. This is fine

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SAS, R and categorical variables

July 13, 2011
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SAS, R and categorical variables

One of the disappointing problems in SAS (as I need PROC MIXED for some analysis) is to recode categorical variables to have a particular reference category. In R, my usual tool, this is rather easy both to set and to modify using the  relevel command available in base R (in the stats package). My understanding

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An enhanced Kaplan-Meier plot

March 8, 2011
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An enhanced Kaplan-Meier plot

We often see, in publications, a Kaplan-Meier survival plot, with a table of the number of subjects at risk at different time points aligned below the figure. I needed this type of plot (or really, matrices of such plots) for an upcoming publication. Of course, my preferred toolbox was R and the ggplot2 package. There

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RStudio: a cut above

March 1, 2011
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RStudio: a cut above

As most followers of R-bloggers.com and the Twitter #rstats know by now, RStudio is a new open-source IDE for R that was beta-released yesterday. I have started putting it through its paces within my R workflow, and my impressions are more than favorable. I also tried it out on my home Linux server in server

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The split-apply-combine paradigm in R

February 25, 2011
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The split-apply-combine paradigm in R

Last night at the DC R Users meetup, which was our largest meetup to date, I gave an introductory presentation on data munging, and spent a bit of time on the split-apply-combine paradigm that I use almost daily in my work. I talked mainly about the packages plyr and doBy, which I use a lot

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ggplot2 joy

February 25, 2011
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ggplot2 joy

I’ve been working on a long-term (25+yr) longitudinal study of rheumatoid arthritis with my boss. He just walked in and asked if I could create a plot showing the trajectory of pain scores over time for each subject, separated by educational level (4 groups). Having now worked with ggplot2 for a while, and learning more

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useR! 2010 done and dusted

July 23, 2010
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useR! 2010 done and dusted

:

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A small customization of ESS

May 14, 2010
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A small customization of ESS

JD Long (at Cerebral Mastication) posted a question on Twitter about an artifact in ESS, where typing “_” gets you “<-”. This is because in the early days of S+, “_” was an allowed assignment operator, and ESS was developed in that era. Later, it was disallowed in favor of “<-” and “=”, so ESS

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Quick and dirty parallel processing in R

April 30, 2010
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Quick and dirty parallel processing in R

R has some powerful tools for parallel processing, which I discovered while searching for ways to fully utilize my 8-core computer at work. What surprised me is how easy it is…about 6 lines of code, if that. Given that I wasn’t allowed to install heavy duty parallel-processing systems like MPICH on the computer, I found

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R amusements

March 5, 2010
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R amusements

On a lark, and to kill a bit of time, I was running the R fortune command looking for references to SAS. Here’s what two successive random fortunes turned up. Can there be two more antipodal opinions about the same product? I laughed out loud. > fortune(‘SAS’) There are companies whose yearly license fees to

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