Yours truly <dieter.menne <at> menne-biomed.de> writes: ... > Recently, a colleague fitted gastric emptying > curves using GraphPad, with 100% success, and > nls failed for one third of these. When we > checked GraphPads output more closely, some of > the coefficients looked like 2.1 with a confidence > interval in the range -27128 ... 314141. Nobody > forces you to look at these, though, when using > GraphPad. >
Since my comment has stirred a bit of an uproar, I should add that this is not the fault of GraphPad, but that most non-linear fitting programs, including those in the big SXXX, give the same results. Harvey Motulsky from Graphpad/Prism informed me that they were going to add special tests in the new versions. Their pdf-manual on nonlinear fitting is worth a look anyway if Bates/Watts is over your head. And if anyone want to see sample data: http://www.menne-biomed.de/gastempt/gastempt1.html > I only wish nls were a little bit more polite in telling me what went wrong. I stand corrected: I only wish nls were less politically correct, but rather inform me WHY it faltered. Dieter ______________________________________________ R-help@stat.math.ethz.ch 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.
