Polynomial function used in fitting nlme curve for observations
polynomial(dat, y, time, degree, raw = TRUE, params = NULL, ...)
subject data to be used
outcome variable
time variable
degree of polynomial
Boolean, use raw polynomials?
NULL
unless user wants to specify starting parameters for gnls
just in case
It's recommended that one uses raw polynomials for this function for numerical stability. As inference is not performed on the parameters themselves, this should have minimial consequences
y ~ mini + (peak - mini) / (1 + exp(4 * slope * (cross - (time)) / (peak - mini)))