practice-safe-paths.qmd

# Practice safe paths {#sec-safe-paths}

Adapt from <https://github.com/jennybc/here_here#readme>.

Include some coverage of fs.

## Use projects and the [here package](https://CRAN.R-project.org/package=here)

How can you avoid `setwd()` at the top of every script?

  * Organize each logical project into a folder on your computer.
  * Make sure the top-level folder advertises itself as such. This can be as simple as having an empty file named `.here`. Or, if you use RStudio and/or Git, those both leave characteristic files behind that will get the job done.
  * Use the `here()` function from the [here package](https://CRAN.R-project.org/package=here) to build the path when you read or write a file. Create paths relative to the top-level directory.
  * Whenever you work on this project, launch the R process from the project's top-level directory. If you launch R from the shell, `cd` to the correct folder first.
  
To continue our example, start R in the `foofy` directory, wherever that may be. Now the code looks like so:


```{r, eval = FALSE}
library(ggplot2)
library(here)

df <- read.delim(here("data", "raw_foofy_data.csv"))
p <- ggplot(df, aes(x, y)) + geom_point()
ggsave(here("figs", "foofy_scatterplot.png"))
```


This will run, with no edits, for anyone who follows the convention about launching R in the project folder. In fact, it will even work if R's working directory is anywhere inside the project, i.e. it will work from sub-folders. This plays well with knitr/rmarkdown's default behavior around working directory and in package development/checking workflows.

Read up on the [here package](https://CRAN.R-project.org/package=here) to learn
about more features, such as additional ways to mark the top directory and
troubleshooting with `dr_here()`. I have also written a [more detailed
paean](https://github.com/jennybc/here_here) to this package before.