Hi Christian,

Thank you very much for the help.
Now I can run. But my main interest is on the region of x[-200 to +200]
and as you can see this logistic regression not fit very well.

You think that using other package / function I can get better fit of these
data?

Best wishes,

miltinho
brazil-toronto

sp.coredep.attr<-read.table(stdin(), head=T, sep=",")
species,dst,preference,probdye
coredep,-7500,1,0.001
coredep,-1000,0.95,0.002
coredep,-500,0.9,0.003
coredep,-250,0.8,0.005
coredep,-120,0.7,0.01
coredep,-100,0.5,0.02
coredep,-90,0.3,0.03
coredep,-60,0.2,0.05
coredep,-30,0.15,0.065
coredep,0,0.1,0.08
coredep,30,0.09,0.1
coredep,60,0.08,0.15
coredep,90,0.07,0.2
coredep,120,0.06,0.3
coredep,240,0.05,0.4
coredep,500,0.04,0.5
coredep,1000,0.02,0.6
coredep,7500,0.01,0.7


plot(preference~as.factor(dst), data=sp.coredep.attr, type="n", cex=0.001,
col="transparent", xlab="Distance (m)", main="CORE Dependent")
lines(sp.coredep.attr$preference, type="b", lwd=2, col="blue")
abline(v=10, col="blue", lty=3)
text(10, 1, "EDGE", cex=1.5)
text(7, 1, "CORE", cex=1.5, col="green")
text(13, 1, "MATRIX", cex=1.5, col="red")
text(4,0.65, "Preference", col="blue")
text(16,0.65, "Prob.Die", col="red")
lines(sp.coredep.attr$probdye, type="b", lwd=2, col="red", lty=2)
require(drc)
sp.coredep.attr.m1 <- drm(preference~dst, data=sp.coredep.attr, fct=L.4())
x11()
plot(sp.coredep.attr.m1, log = "")
x11()
plot(sp.coredep.attr.m1, log = "", xlim = c(-500, 500), ylim = c(0, 1))
summary(sp.coredep.attr.m1)






On Thu, Apr 23, 2009 at 1:41 AM, Christian Ritz <ritz@life.ku.dk> wrote:

> 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
>
>

	[[alternative HTML version deleted]]


