Questions: missing data behavior, general advice

[alexpghayes]

Missing data behavior

Does prediction provide any guarantees about predictions on missing data? I've been playing around some and it seems like most methods behave like predict() with na.action = na.pass. Is this tested/guaranteed?

I'm currently reworking the augment() methods for broom and am considering moving to prediction as a backend, but need to guarantee that data doesn't get silently dropped.

General advice for predictions

Do you have any general advice for developers implementing predict() methods?

I'm gathering suggestions for R model package development at https://github.com/alexpghayes/principles (currently just rough notes), and if you'd be willing to share your thoughts on what makes a predict() method easy to work with, I'd love to write that up.

[leeper]

prediction() doesn't per se do anything. The na.action is actually handled by find_data() (in the default case) here: https://github.com/leeper/prediction/blob/master/R/find_data.R#L48-L51 I really haven't tested that much.

On the second point, I think we need standardization of model objects so that predict()'s default method just works. Lacking that, type safety seems the most critical (like the main example in the README here).

[alexpghayes]

Gotcha.

Do you have any particular pain points in terms of standardization? We're brainstorming some at tidymodels/parsnip#41.