polynomial {bdots}

Polynomial curve function for nlme

Description

Polynomial function used in fitting nlme curve for observations

Usage

polynomial(dat, y, time, degree, raw = TRUE, params = NULL, ...)

Arguments

dat

subject data to be used

y

outcome variable

time

time variable

degree

degree of polynomial

raw

Boolean, use raw polynomials?

params

NULL unless user wants to specify starting parameters for gnls

...

just in case

Details

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)))