get_rsplit() helper to extract split objects?

[mikemahoney218]

Feature

Hi all!

Right now, I believe the best way for users to get individual rsplit objects from an rset is to index into the rset themselves:

library(rsample)

ex_vfold <- vfold_cv(Orange, v = 2)
ex_vfold$splits[[1]]
#> <Analysis/Assess/Total>
#> <17/18/35>

I'm wondering if it would be useful to provide a helper function, get_rsplit() or similar, to extract these? My personal interest is in making the spatialsample documentation a bit cleaner (because autoplot() has separate methods for rset and rsplit objects), but I think it might also be a friendlier interface overall:

get_rsplit <- function(rset, n, ...) {
  UseMethod("get_rsplit")
}

get_rsplit.rset <- function(rset, n, ...) rset$splits[[n]]

get_rsplit.default <- function(rset, n, ...) {
  cls <- paste0("'", class(x), "'", collapse = ", ")
  rlang::abort(
    paste("No `get_rsplit()` method for this class(es)", cls)
  )
}

get_rsplit(ex_vfold, 1)
#> <Analysis/Assess/Total>
#> <17/18/35>

Thanks!

[hfrick]

I think this might not exist yet because rsplit objects (other than those from initial_split() and friends) are not generally meant to be used standalone.

That said, I wouldn't mind such functionality for illustration purposes. Do you want to make a PR for that?

If so, could you please

• call the arg index instead of n
• add a dot prefix to the name since it's more developer-focussed, so .get_rsplit()
• add @keyword internal

[mikemahoney218]

Happy to add a PR! That said, we use this pattern a lot in long-form user-facing documentation, across rsample, the tidymodels website, TMwR, and spatialsample (and possibly elsewhere, these are the only spots I checked):

https://rsample.tidymodels.org/articles/rsample.html#individual-resamples-are-rsplit-objects
https://rsample.tidymodels.org/articles/Applications/Recipes_and_rsample.html
https://rsample.tidymodels.org/articles/Working_with_rsets.html#model-assessment

https://www.tidymodels.org/learn/work/nested-resampling/
https://www.tidymodels.org/learn/models/time-series/

https://www.tmwr.org/resampling.html
https://www.tmwr.org/dimensionality.html

https://spatialsample.tidymodels.org/
https://spatialsample.tidymodels.org/articles/spatialsample.html
https://spatialsample.tidymodels.org/articles/buffering.html

Also once in parsnip:
https://parsnip.tidymodels.org/articles/Submodels.html

I think it's also in a good number of function examples.

So I'd suggest that this should be a user-facing helper as well, and not just a developer function (so no . prefix and no @keyword internal). Happy to make it internal if you disagree, though.

[hfrick]

Oye! You got me convinced 😄 get_rsplit() it is!

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