get_halflife_points method for PKNCAdata

[Gero1999]

No description provided.

[billdenney]

I think that this can be simplified to something like:

group_cols <- names(getGroups(object))
object$intervals <- object$intervals[, c(group_cols, "start", "end", "half.life")]

[Gero1999]

When groups are not specified in the intervals and I try to do this:

  cols_to_keep <- intersect(names(object$intervals), c("start", "end", "half.life"))
  object$intervals <- object$intervals[, cols_to_keep]
  object$intervals <- unique(object$intervals)
  o_nca <- pk.nca(object)

I get the next error:

Error in purrr::pmap(.l = list(data_conc = splitdata$data_conc, data_dose = splitdata$data_dose,  : 
  ℹ In index: 1.
Caused by error in `if (interval[[n]]) ...`:
! Please report a bug.
: Error with interval start=0, end=Inf: argument is of length zero

Instead, I simplified by making FALSE other parameters:

  params_to_ignore <- setdiff(names(get.interval.cols()), c("half.life", "start", "end"))
  object$intervals[, params_to_ignore] <- FALSE

PS: Making them NA did not work either, so I just kept it simple as this does not affect the generation of the half.life result.

[billdenney]

I wanted to check how one thing worked, and it worked as I expected (great work!).

Merging when the tests complete.