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...rticular should treat 0 and 1 "symmetrically" and I find it ugly that the previous fixup (our two ominous lines) is not at all symmetric wrt 1/2, notably the 2nd transformation is made unconditionally but the first one not. Fortunately, the same source file, <R>/src/library/stats/R/zzzModels.R also defines the SSfpl() == 4-parameter logistic model and there, the 'init' function needs to do the same scaling to (0, 1) and does it much nicer, indeed (anti)symmetrically. I'm looking into using that in SSlogis() as well, fixing this bug. Martin Maechler ETH Zurich and R...

...and 1 > "symmetrically" and I find it ugly that the previous fixup (our two ominous > lines) is not at all symmetric wrt 1/2, notably the 2nd transformation is made > unconditionally but the first one not. > > Fortunately, the same source file, <R>/src/library/stats/R/zzzModels.R > also defines the SSfpl() == 4-parameter logistic model > > and there, the 'init' function needs to do the same scaling to (0, 1) and does it > much nicer, indeed (anti)symmetrically. > > I'm looking into using that in SSlogis() as well, fixing this bug. > &g...

Hi Keep your messages in the list, you increase your chance to get some answer. I changed your data to groupedData object (see below), but I did not find any problem in it. plot(wlg) gives reasonable picture and I am not such expert to see any problem with data. Seems to me, that something has to be wrong with nlsList function. > wheat.list <- nlsList(Prop ~ SSlogis(end,Asym, xmid,