A self-starting nonlinear regression function for the one-compartment
open model with first-order absorption and elimination. The parameters
to be fit are lCl, lka, and lke. An expression for the model is
USAGE:
first.order.log(Dose, time, lCl, lka, lke)
REQUIRED ARGUMENTS:
Dose:
the initial dose received at time zero.
time:
the "independent" variable, usually the time since the initial dose
was received.
lCl:
the parameter giving the log of the clearance.
lka:
the parameter giving the log of the absorption rate constant.
lke:
the parameter giving the log of the elimination rate constant.
VALUE:
The predicted responses are returned. The gradient attribute is
a length(time) by 3 matrix containing the derivatives of the predicted
responses with respect to the parameters lCl, lka, and lke.
DETAILS:
The function was created by applying deriv() to the expression
Dose * exp(lka) * exp(lke) * (exp(-exp(lke) * time) - exp(-exp(lka) *
time)) / (exp(lCl) * (exp(lka) - exp(lke))). An initial attribute was
added to calculate the starting estimates for the parameters
automatically.