getGroups() function on PKNCAresults object

[Gero1999]

When we perform the getGroups(PKNCAresult) the output shows the groups for the concentration group columns and the start variable (level = 2 / default). However, I noticed the end is not considered. I am just curious on what is the theoretical reason behind this!

# Load necessary library
library(PKNCA)

# Simplified concentration dataset
conc_data <- data.frame(
  subject = 1,
  time = c(-0.05, 1, 2, 3),
  conc = c(2, 2, 1, 0.5)
)

# Example dose dataset
dose_data <- data.frame(
  subject = c(1),
  time = c(0),
  dose = c(100)
)

# Create PKNCAconc and PKNCAdose objects
conc_obj <- PKNCAconc(conc_data, formula = "conc ~ time | subject")
dose_obj <- PKNCAdose(dose_data, formula = "dose ~ time | subject")

# Define intervals
intervals <- data.frame(
  start = c(0, 0),
  end = c(2, 2),
  half.life = c(TRUE, FALSE),
  tmax = c(FALSE, TRUE),
  impute = c("start_predose", NA_character_)
)

# Convert data to a PKNCAdata object
data_obj <- PKNCAdata(conc_obj, dose_obj, intervals = intervals)

# Run the NCA
PKNCAres <- pk.nca(data_obj)
print(getGroups(PKNCAres))

The output for me is:

# A tibble: 11 × 2
   subject start
     <dbl> <dbl>
 1       1     0
 2       1     0
 3       1     0
 4       1     0
 5       1     0
 6       1     0
 7       1     0
 8       1     0
 9       1     0
10       1     0
11       1     0

[billdenney]

I don't recall a reason for this, and thinking about it now, I don't think it makes sense. I'll change it to include start and end.