Dear R users I'm a new user of R and I have a basic question about the 4-parameter logistic model. According to the information from Pinheiro & Bates the model is:
y(x)=theta1+(theta2-theta1)/(1+exp((theta3-x)/theta4)) == y(x)=A+(B-A)/(1+exp((xmid-input)/scal)) from the graph in page 518 of the book of the same authors (mixed models in S) theta 1 corresponds to the horizontal asymptote as x goes to infinity and theta2 the horizontal asymptote as x goes to -infinity. When I use the function SSfpl(input,A,B,xmid,scal), I'm not sure why the value of A is the lower of the two asymptotes if according to the original function A should be equal to theta1 (upper asymptote).. or maybe I'm wrong. I'll appreciate any comment on this. Best Regards CM ______________________________________________ [EMAIL PROTECTED] mailing list http://www.stat.math.ethz.ch/mailman/listinfo/r-help
