Fix IV bolus calculations not to require time = 0

[billdenney]

C0 should be imputed here automatically

library(PKNCA)
#> 
#> Attaching package: 'PKNCA'
#> The following object is masked from 'package:stats':
#> 
#>     filter

d_iv <- data.frame(conc = c(4, 2, 1, 0.45), time = c(5, 15, 30, 60))
d_intervals <- data.frame(start = 0, end = Inf, aucivinf.obs = TRUE)
o_conc <- PKNCAconc(data = d_iv, conc~time)
o_data <- PKNCAdata(o_conc, intervals = d_intervals)
o_nca <- pk.nca(o_data)
#> No dose information provided, calculations requiring dose will return NA.
#> Warning in pk.calc.c0(conc = c(4, 2, 1, 0.45), time = c(5, 15, 30, 60), :
#> time.dose is NA
#> Warning: Requesting an AUC range starting (0) before the first measurement (5)
#> is not allowed
as.data.frame(o_nca)
#> # A tibble: 14 × 5
#>    start   end PPTESTCD            PPORRES exclude                              
#>    <dbl> <dbl> <chr>                 <dbl> <chr>                                
#>  1     0   Inf c0                  NA      <NA>                                 
#>  2     0   Inf tmax                 5      <NA>                                 
#>  3     0   Inf tlast               60      <NA>                                 
#>  4     0   Inf clast.obs            0.45   <NA>                                 
#>  5     0   Inf lambda.z             0.0322 <NA>                                 
#>  6     0   Inf r.squared            0.978  <NA>                                 
#>  7     0   Inf adj.r.squared        0.956  <NA>                                 
#>  8     0   Inf lambda.z.time.first 15      <NA>                                 
#>  9     0   Inf lambda.z.n.points    3      <NA>                                 
#> 10     0   Inf clast.pred           0.431  <NA>                                 
#> 11     0   Inf half.life           21.5    <NA>                                 
#> 12     0   Inf span.ratio           2.09   <NA>                                 
#> 13     0   Inf aucinf.obs          NA      Requesting an AUC range starting (0)…
#> 14     0   Inf aucivinf.obs        NA      Requesting an AUC range starting (0)…

^{Created on 2025-01-03 with reprex v2.1.1}