I had to go shopping for a family birthday and new apartment stuff this past weekend. I entered the big, bright department store and froze, with instant regret and dread, because I heard the foreboding sounds of this phenomenon:
Now I don’t know about other countries, but in America the tinsel-laden commercial Christmas season stretches starts the day they break down the pop-up Halloween shops and eventually consumes all of popular culture for two months.

This function feeds a high-amplitude sine function through a logit, offsetting so as to have the pulse start and stop at arbitrary times. It has an integral of one per period for large \(L\).
\[f(t) = \frac{c}{a - b} \frac{1}{1 + e^{L \left(sin(2\pi((t-a)/c + \xi)) - sin(2\pi\xi)\right)} }\]
where
\[\begin{aligned} t &= \text{time} \\ a &= \text{time at start of pulse} \\ b &= \text{time at end of pulse} \\ c &= \text{period length} \\ a &< b < c \\ L &= \text{an arbitrarily large number} \\ \xi &= \frac{3}{4} - \frac{b - a}{2c} \\ \end{aligned}\]

Last Friday at the Davis R Users’ Group, Mallory Johnson gave a presentation on RQDA, an R-based GUI tool for doing coding on documents for use in qualitative text analysis. Here’s the video, and you can view the slides here.

*[Sorry about reverb in the video]*

Last Friday at the Davis R Users’ Group, Grace Charles gave a presentation on structural equation modeling in R using the **Lavaan** package. Here’s the video and her slides. We’ve also posted Grace’s script from the presentation as a gist here. More resources that Grace mentioned in her talk below.

Last Fr Davis R Users’ Group, Jaime Ashander gave a presentation on and visualizing and diagnosing (G)LMMs in R. Here’s the video:
Jaime also wrote up the notes from his talk, including all the code, on his blog here (with the raw R Markdown file on github here). The material in the blog post is expanded and improved upon from the original talk, though this means the video and posted code don’t match exactly.