# Putting the R in romantic

I've used R for a lot of tasks unrelated to statistics or data analysis. For example, it's usually a lot easier for me to write an intelligent batch file/folder renamer or copier as an R script than a bash shell script.

Earlier today I made a collection of photos that I wanted to put on a digital picture frame to mail to my partner. I also made a set of messages that I wanted to show up randomly. What I needed to do was to shuffle the set of 260+ images in such a way that a subset of them would not show up consecutively.

To make referencing the images easier, let's call the overall set of $n$ images $Y$ (with $Y = y_1, \ldots, y_n$), and let $X \subset Y$ be the images we do not want to have consecutive pairs of after the shuffling. Let $Y' = y_{(1)}, \ldots, y_{(n)}$ be the shuffled set of images.

This was really easy to accomplish in R. I started with k <- 0; set.seed(k) and shuffled all the images (using sample.int()). Then I checked whether our very specific requirement was or was not met.

If we did end up with a pair of consecutive images from $X$, we increment $k$ by 1 and repeat the procedure until $\{y_{(i-1)}, y_{(i)}\} \not\subset X ~\forall~i = 2, \ldots, n$.

I think what makes R really nice to use for tasks like this is vectorized functions and binary operators like which(), %in%, order(), duplicated(), sample(), sub(), and grepl(), as well as data.frames that you can expand to include additional data, such as indicators of whether row $m$ is related to row $m-1$.

Next time you have to do something on the computer that is repetitive and time-consuming, I urge you to consider writing a script/program to do it for you if you know R but haven't considered it before for doing file organization.

Cheers~