bind_draws() for lists of draws objects

[mjskay]

Over the past week or two I have encountered multiple instances when helping some folks with {posterior} where I wished bind_draws() had an implementation for lists. See, for example, this bit of code from here:

betas_dfs = lapply(anes_2012_models, function(m) posterior::as_draws_df(t(m$beta)))
betas_df = do.call(posterior::bind_draws, c(betas_dfs, list(along = "draw")))

Basically, the issue is that if you have a list of draws objects like betas_dfs and want to bind them together along something other than variables (along = "variable" is the default for bind_draws()), you have to make a fairly ugly construction with do.call().

The alternative is to allow arguments to bind_draws() to be draws objects or lists of draws objects (similar to how dplyr::bind_rows() works on data frame or lists of data frames). Then the second line above could just be:

betas_df = posterior::bind_draws(betas_dfs, along = "draw")

[paul-buerkner]

I like the option of supporting lists of draws objects.