Feature Request: Allow assignment of NA to Errors

[billdenney]

I need to represent a change from baseline and change from placebo in the same table. Generally, I'd like to see values that look like the following:

> change_from_baseline_change_from_placebo <- set_errors(1:3, 1:3)
> change_from_baseline_change_from_placebo[1] <- NA
Error in UseMethod("errors") : 
  no applicable method for 'errors' applied to an object of class "logical"
> change_from_baseline_change_from_placebo[1] <- set_errors(x=NA_real_, value=NA)
> change_from_baseline_change_from_placebo
Errors: NA  2  3
[1] NA  2  3
> 

It would be handy to have a function for errors.logical like:

errors.logical <- function(x) {
  if (all(is.na(x))) {
    set_errors(as.real(x), NA)
  } else {
    stop("logical vectors must be `NA` to be coerced into errors")
  }
}

[Enchufa2]

Thanks!