Knit from the command line

Knitr is a great way to combine document markup (Latex, Markdown, HTML, etc.) with R code for data analysis and visualization. It pulls out the chunks of R code, runs them, and re-inserts the results into the document source (usually a .tex file), which can then be compiled as usual. Normally you would call it from an R console (or use something like RStudio), but what if you want to call it from the command line, like latex?  Here’s a little shell script that I use to automate the knitting of .Rnw files (combining R and Latex): knit.sh.

It call knit() inside R, then runs pdflatex on the resulting file. It is very simple to use (you must of course have the knitr package installed in R):
knit.sh awesomefile.Rnw

This would produce awesomefile.pdf (as well as the intermediate file awesomefile.tex, and the extracted R commands, awesomefile.R). You might even rename the script as knit and put it somewhere on your search path (maybe /usr/local/bin/) to be even more fancy.

Collect keyboard responses asynchronously in Javascript

Some of our Mechanical Turk experiments are written in straight-up javascript, which gives you a lot of control and flexibility but at the expense of having to write some pretty basic functionality from scratch.  I recently was in a situation where I wanted to collect separate keyboard responses in different but possibly overlapping time windows: stimuli are coming in fast and on some of them, the subject needs to press the spacebar.  Rather than fix my design so that the response windows would never overlap, I decided to write a function that would collect a one-off keyboard response, asynchronously, meaning that other experiment control code can run behind it.