Bug: PKNCA imputations do not disconsider observed parameters

[Gero1999]

Description

There are parameters (i.e, cmax, tmax) that should be based merely on observations, and not imputed data. At first we though that this was controlled by PKNCA, but it is not, so it is a bug that eventually will need to be solved by PKNCA. In the meantime, as a temporary measure we will develop a solution for this problem that is external to the package.

Suggested solution
Make a function that only and simply modifies the PKNCAdata$intervals, i.e, remove_impute_for_params(PKNCAdata, params). The function identifies rows/intervals where param = TRUE & !is.na(impute), set in those param = FALSE and create duplicates where param = TRUE, impute = NA

To reproduce

Run NCA on IV bolus data in both conditions: considering t0 and not considering it. You can see that, erroneously, C0 and t0 values change in each run!

Expected behaviour

t0 and c0 should in any case change when imputations are added