Hi: I have data from an assay in the form of two vectors, one is response and the other is a predictor. When I attempt to fit a 5 parameter logistic model with "nls", I get converged parameter estimates. I also get the same answers with "gnls" without specifying the "weights" argument.
However, when I attempt to use the "gnls" function and try to estimate the variance function, as a power function, I get the following error message: > ans51g <- gnls(log(b51) ~ p0 + p1/(1 + exp(-(log(dose)-p2)/p3))^p4, start=list(p0=3,p1=1,p2=4,p3=2,p4=1.5),control=gnlsControl(tol=1.e- 07),weights=varPower()) Error in eval(expr, envir, enclos) : Object "." not found > What am I doing wrong here and how can I do a GLS analysis with a variance function that is estimated from the data? Here is my data: > b51 <- c(17447.60674, 7060.37234, 2872.53012, 796.40426, 454.47222, 260.22340, 120.11905, 83.40196, 51.45745, 36.87912, 26.73256, 25.18681, 17.97674) > dose <- c( 1.000000e+04, 1.000000e+03, 2.500000e+02, 6.250000e+01, 3.125000e+01, 1.562500e+01, 7.812500e+00, 3.906250e+00, 1.953125e+00, 9.765625e-01, 4.882813e-01, 2.441406e-01, 1.000000e-03) thanks for the help, Ravi. ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
