On Sun, May 25, 2008 at 9:32 PM, Katharine Mullen <[EMAIL PROTECTED]> wrote: > Dear Spencer, > > I just saw your post. > > If the singular gradient happens during or after iteration one (that is, > not at the initial estimates), then calling summary on the nls output > would give standard error estimates on the parameters useful for > diagnostics. You could also call chol2inv(xx$m$Rmat()) where xx is the > object returned by nls to get an estimate of the inverse of the hessian; > you could use this estimate to proceed with the diagnostics you were > discussing.
Try this: > library(nls2) > DF1 <- data.frame(y=1:9, one=rep(1,9)) > xx <- nls2(y~(a+2*b)*one, DF1, start = c(a=1, b=1), algorithm = "brute-force") > eigen(chol2inv(xx$m$Rmat())) $values [1] 5.070602e+31 0.000000e+00 $vectors [,1] [,2] [1,] -0.8944272 -0.4472136 [2,] 0.4472136 -0.8944272 ______________________________________________ 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.