W1.4 {drc} | R Documentation |
'W1.4' and 'W2.4' provide the four-parameter Weibull functions, self starter function and names of the parameters.
W1.4(fixed = c(NA, NA, NA, NA), names = c("b", "c", "d", "e")) W2.4(fixed = c(NA, NA, NA, NA), names = c("b", "c", "d", "e"))
fixed |
numeric vector. Specifies which parameters are fixed and at what value they are fixed. NAs for parameter that are not fixed. |
names |
a vector of character strings giving the names of the parameters. The default is reasonable. |
The equations for the mean functions are given at weibull1
.
See weibull1
.
This function is for use with the model fitting function drm
.
Christian Ritz
Seber, G. A. F. and Wild, C. J (1989) Nonlinear Regression, New York: Wiley & Sons (pp. 330–331).
Setting c=0 yields W1.3
. A more flexible function, allowing
fixing or constraining parameters, is available through weibull1
.
## Fitting a four-parameter Weibull (type 1) model terbuthylazin.m1 <- drm(rgr~dose, data = terbuthylazin, fct = W1.4()) summary(terbuthylazin.m1)