[R] fitting assimptotic decaing with - and + on X

[Christian Ritz]

Hi Milton,

you're right that most of the functions in the package "drc" are suited for
sigmoidal/s-shaped curves defined on the positive axis.

However, there is one exception: the logistic model:

library(drc)

sp.coredep.attr.m1 <- drm(preference~dst, data=sp.coredep.attr, fct=L.4())

plot(sp.coredep.attr.m1, log = "")
plot(sp.coredep.attr.m1, log = "", xlim = c(-500, 500), ylim = c(0, 1))

summary(sp.coredep.attr.m1)


The fit isn't very good, possibly because the curve you've observed seems to have a kind
of bent at or close to 0.

Christian