Dear all, I have a question on the four parameter logistic regression. Not sure about how to set the start values for the parameters. Can anyone familiar with this give some hint? Thanks so much.
Hannah For example, suppose I have the following data values, > temp mean_std [1,] 0.0 139 [2,] 0.5 142 [3,] 1.0 143 [4,] 2.0 145 [5,] 4.0 155 [6,] 7.0 169 [7,] 15.0 184 [8,] 30.0 220 [9,] 60.0 242 [10,] 150.0 269 [11,] 300.0 283 [12,] 600.0 289 [13,] 1500.0 291 [14,] 3000.0 299 [15,] 10000.0 299 logitfit <- nls(log(mean_std) ~ A+(B-A)/(1+(std[,1]/C)^scal), data=temp, start=list(A=3.5, B=15, C=600, scale=2.5)) These starting values are not working! [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.