Articles by Dan Mirman

A little growth curve analysis Q&A

June 8, 2015 | Dan Mirman

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:... [Read more...]

Plotting Factor Analysis Results

April 20, 2015 | Dan Mirman

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 ... [Read more...]

How to learn R: A flow chart

February 23, 2015 | Dan Mirman

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...
[Read more...]

My "Top 5 R Functions"

February 2, 2015 | Dan Mirman

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... [Read more...]

Guidebook for growth curve analysis

March 3, 2014 | Dan Mirman

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 ... [Read more...]

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

February 11, 2014 | Dan Mirman

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. ... [Read more...]

New version of lme4

September 30, 2013 | Dan Mirman

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... [Read more...]

Multiple pairwise comparisons for categorical predictors

April 5, 2013 | Dan Mirman

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 ... [Read more...]

Using R to create visual illusions

January 18, 2013 | Dan Mirman

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... [Read more...]

Plotting model fits

August 29, 2012 | Dan Mirman

We all know that it is important to plot your data and explore the data visually to make sure you understand it. The same is true for your model fits. First, you want to make sure that the model is fitting the data relatively well, without any substantial systematic deviations. ... [Read more...]

Customizing ggplot graphs

August 7, 2012 | Dan Mirman

There are many things I love about the R package ggplot2. For the most part, they fall into two categories:The "grammar of graphics" approach builds a hierarchical relationship between the data and the graphic, which creates a consistent, int... [Read more...]

Crawford-Howell (1998) t-test for case-control comparisons

August 6, 2012 | Dan Mirman

Cognitive neuropsychologists (like me) often need to compare a single case to a small control group, but the standard two-sample t-test does not work for this because the case is only one observation. Several different approaches have been proposed and in a new paper just published in Cortex, Crawford and ... [Read more...]

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