should remove_variables be exported? about posterior

[paul-buerkner]

I think we can export the generic and thus the methods actually. However, then we would have to add all kinds of validity checks, which we currently don't have in place there. I like the idea of adding an exclude option to subset_draws.
This could internally call remove_variables then.

BTW: the fact that the remove_variables methods are exported just ensures that they are registered as S3 methods to the generic. They won't actually be exported this way.

[paul-buerkner]

Yes, that looks sensible to me. Thank you!

[n-kall]

I think an exclude option for subset_draws could be implemented with setdiff like this. If this seems ok, I can make a PR

subset_draws.draws_array <- function(x, variable = NULL, iteration = NULL,
                                     chain = NULL, draw = NULL, regex = FALSE,
                                     unique = TRUE, exclude = FALSE, ...) {
  if (all_null(variable, iteration, chain, draw)) {
    return(x)
  }

  x <- repair_draws(x)
  variable <- check_existing_variables(variable, x, regex = regex)
  iteration <- check_iteration_ids(iteration, x, unique = unique)
  chain <- check_chain_ids(chain, x, unique = unique)
  draw <- check_draw_ids(draw, x, unique = unique)

 ########## code for exclude option
  if (exclude) {
    if (!is.null(variable)) {
      variable <- setdiff(variables(x), variable)
    }
    if (!is.null(iteration)) {
      iteration <- setdiff(iteration_ids(x), iteration)
    }
    if (!is.null(chain)) {
      chain <- setdiff(chain_ids(x), chain)
    }
    if (!is.null(draw)) {
      draw <- setdiff(draw_ids(x), draw)
    }
  }
 #############

  x <- prepare_subsetting(x, iteration, chain, draw)
  if (!is.null(draw)) {
    iteration <- draw
  }
  x <- .subset_draws(x, iteration, chain, variable, reserved = TRUE)
  if (!is.null(chain) || !is.null(iteration)) {
    x <- repair_draws(x, order = FALSE)
  }
  x
}

[n-kall]

Closed by #336