# Blog Archives

## A little growth curve analysis Q&A

June 8, 2015
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I had an email exchange with Jeff Malins, who asked several questions about growth curve analysis. I often get questions of this sort and Jeff agreed to let me post excerpts from our (email) conversation. The following has been lightly edited for clarity and to be more concise.Jeff asked:I’ve fit some curves for accuracy data...

## Plotting Factor Analysis Results

April 20, 2015
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A recent factor analysis project (as discussed previously here, here, and here) gave me an opportunity to experiment with some different ways of visualizing highly multidimensional data sets. Factor analysis results are often presented in tables of factor loadings, which are good when you want the numerical details, but bad when you want to...

## How to learn R: A flow chart

February 23, 2015
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I often find myself giving people suggestions about how to learn R, so I decided to put together a flow chart. This is geared toward typical psychology or cognitive science researchers planning to do basic data analysis in R. This is how to get started...

## My "Top 5 R Functions"

February 2, 2015
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In preparation for a R Workgroup meeting, I started thinking about what would be my "Top 5 R Functions". I ruled out the functions for basic mechanics - save, load, mean, etc. - they're obviously critical, but every programming language has them, so th...

## Plotting mixed-effects model results with effects package

August 13, 2014
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As separate by-subjects and by-items analyses have been replaced by mixed-effects models with crossed random effects of subjects and items, I've often found myself wondering about the best way to plot data.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...

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

April 4, 2014
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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...

## Guidebook for growth curve analysis

March 3, 2014
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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 ...

## 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...

## 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...

## 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...