Calculate the (observed oral) clearance
Details
cl is dose/auc.
If dose is the same length as the other inputs, then the output
will be the same length as all of the inputs; the function assumes that you
are calculating for multiple intervals simultaneously. If the inputs other
than dose are scalars and dose is a vector, then the function assumes
multiple doses were given in a single interval, and the sum of the doses
will be used for the calculation.