RXR-1851: add function to calculate auc pre-ss

[roninsightrx]

This adds a convenience function to calculate AUC (and conc) using linear models, based on just the PK parameters.

[jasmineirx]

lgtm

one consideration is that this requires standard mapping of doses into the first compartment, and so won't support drugs like tacrolimus where we often have a mix of oral/iv dosing. do you think it makes sense to add some documentation or warnings somewhere? one option could be to check reg for multiple type arguments. the user is more likely to be aware of the limitation if supplying dose/interval/t_inf since the "type" argument is not present.

[jasmineirx]

it would be tidier to put the parameters argument second, since then you can pass arguments by position more conveniently

calc_auc_analytic("1cmt_iv_bolus", pars, reg)
calc_auc_analytic("1cmt_iv_bolus", pars, dose = 1000, interval = 24, t_inf = 1)

[jasmineirx]

Suggested change

	if(is.null(t_inf) || t_inf == 0) t_inf <- 1e-6
	if(is.null(t_inf) || any(t_inf == 0)) t_inf[t_inf > 0] <- 1e-6

t_inf can be of length > 1. the suggested code handles this situation.

[roninsightrx]

I actually intended it to be a single value, like dose and amount, that just specify the ongoing regimen. I will make that more clear in the code.

[roninsightrx]

lgtm

one consideration is that this requires standard mapping of doses into the first compartment, and so won't support drugs like tacrolimus where we often have a mix of oral/iv dosing. do you think it makes sense to add some documentation or warnings somewhere? one option could be to check reg for multiple type arguments. the user is more likely to be aware of the limitation if supplying dose/interval/t_inf since the "type" argument is not present.

Right now it can only be used for iv models, so it shouldn't be an issue. The linear oral models in PKPDsim don't calculate AUC.

[jasmineirx]

lgtm