A few helpers for working with the {targets} package in R.

|

tags:

I started to use the {targets} package for some of my larger projects. It was a little challenging for me to wrap my head around but after working through some initial problems I think it will help me stay organized and write code in a more composable way. Below are a few notes that I needed to keep coming back to when I was getting started. If you need a comprehensive {targets} getting started I suggest the targets book linked above or in the References section below.

Start a {targets} project

In an empty or existing R project directory run:

targets::use_targets()

The most important targets commands to remember

tar_make() ## Runs your targets workflow
tar_load_everything() ## loads targets so you can view and work with them. 
tar_manifest() ## overview of your targets
tar_visnetwork() ## a visual tree of your targets
tar_delete(name_of_target) ## deletes 'name_of_target' target.

VS code keyboard shortcuts

Below are a few keybindings I added to VS Code. They run tar_make() with control+shift+M and tar_load_everything() with control+shift+L in the terminal. These are the commands that I use the most. add the following to your VS Code json (ctrl+shift+p and search "keybindings json").

{
    "key": "ctrl+shift+m",
    "command": "workbench.action.terminal.sendSequence",
    "args": {
        "text": "tar_make()\u000D"
    }
},
{
    "key": "ctrl+shift+l",
    "command": "workbench.action.terminal.sendSequence",
    "args": {
        "text": "tar_load_everything()\u000D"
    }
}

Outputing a file

In your _targets.R list():

list(
    ##>>>> Other targets above making data...
    tar_target(output, output_func(data, output_path), format="file")
)

And then your function file in the /R directory would look like this:

output_func<-function(data, output_path){
    write_csv(data, output_path)
    output_path ## you must return an output path so that the file can be tracked. 
}

Rmarkdown

To start using Rmarkdown you need the {tarchetypes} package. Load it right under the {targets} package in your _targets.R file with library(tarchetypes).

Then to render a Rmarkdown documents in your targets list you can use tar_render().

list(
  ## More targets above
  tar_render(documantation, "Rmd/documentation.Rmd")
  ## More targets
)

Within the Rmarkdown file things are a little different. The two I've used the most are:

tar_read(name_of_target) ## Loads an R object such as a tibble or sf object.
tar_load(name_of_target) ## Loads a plot for example.

Spatial Rasters from the {tera} package had problems

One problem I had with working with targets is, I work with a lot of spatial grid data. I've been using the [{terra}] package as my go to grid package. However a bit stumbling block for me was you can't write a SpatialRaster as a targets object. Or at least I couldn't figure out how. I put up a question on Stack Exchange and the terra package maintainer was kind enough to respond. But we never got to a resolution.

I also reached out on Mastadon and Miles McBain, Targets evangelist, was kind enough to get back to me, but also no resolution.

Well that all for now.

References