Blog Archives

Plotting mixed-effects model results with effects package

August 13, 2014
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Plotting mixed-effects model results with effects package

As separate by-subjects and by-items analyses have been replaced by mixed-effects models with crossed random effects of subjects and items, I've often found myself wondering about the best way to plot data. The simple-minded means and SE from trial-lev...

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Flip the script, or, the joys of coord_flip()

April 4, 2014
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Flip the script, or, the joys of coord_flip()

Has this ever happened to you?I hate it when the labels on the x-axis overlap, but this can be hard to avoid. I can stretch the figure out, but then the data become farther apart and the space where I want to put the figure (either in a talk or a paper...

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Guidebook for growth curve analysis

March 3, 2014
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Guidebook for growth curve analysis

I don't usually like to use complex statistical methods, but every once in a while I encounter a method that is so useful that I can't avoid using it. Around the time I started doing eye-tracking research (as a post-doc with Jim Magnuson), people were ...

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Three ways to get parameter-specific p-values from lmer

February 11, 2014
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How to get parameter-specific p-values is one of the most commonly asked questions about multilevel regression. The key issue is that the degrees of freedom are not trivial to compute for multilevel regression. Various detailed discussions can be found on the R-wiki and R-help mailing list post by Doug Bates. I...

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New version of lme4

September 30, 2013
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If you haven't realized it yet, a new version of lme4 (version 1.0-4) was released recently (Sept. 21). For an end-user like me, there were not many changes, but there were a few:No more using the @ operator. After a very helpful email exchange with Be...

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A function for comparing groups on a set of variables

May 16, 2013
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I'm often in the position of needing to compare groups of either items or participants on some set of variables. For example, I might want to compare recognition of words that differ on some measure of lexical neighborhood density but are matched on wo...

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Multiple pairwise comparisons for categorical predictors

April 5, 2013
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Multiple pairwise comparisons for categorical predictors

Dale Barr (@datacmdr) recently had a nice blog post about coding categorical predictors, which reminded me to share my thoughts about multiple pairwise comparisons for categorical predictors in growth curve analysis. As Dale pointed out in his post, the R default is to treat the reference level of a factor as a...

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R 3.0 released; ggplot2 stat_summary bug fixed!

April 4, 2013
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The new version of R was released yesterday. As I understand it, the numbering change to 3.0 represents the recognition that R had evolved enough to justify a new number rather than the addition of many new features. There are some important new featur...

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Using R to get h5-index for a list of journals

February 8, 2013
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In my last blog post I wrote about impact factors and h-index for different journals. That got me wondering about what the h5 index is for all of the journals that I read and may want to publish in. I could look them all up individually, but that sound...

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Using R to create visual illusions

January 18, 2013
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Using R to create visual illusions

This brings together two of my favorite (professional) things: R and visual illusions. Aside from being an extremely impressive application of R, it's a cool way of making it clear that the illusion is, in fact, an illusion. Here's a simple example:lib...

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