R help - May 2012 - Error with psi value for 'segmented' package for R

Hi everyone,

while trying to use 'segmented' (R i386 2.15.0 for Windows 32bit OS) to
determine the breakpoint I got stuck with an error message and I can't find
solution. It is connected with psi value, and the error says:



Error in seg.glm.fit(y, XREG, Z, PSI, weights, offs, opz) : 
  (Some) estimated psi out of its range



This is the code I am using:

library("segmented")
curva<-read.table("lamintr1.txt", header=T)
attach(curva)
fit.glm<-glm(gpp~temp, weight=NULL, family=gaussian)
plot(temp,gpp,xlab=expression("temp"),
ylab="gpp",pch=15,cex=0.8,xlim=c(0,50), ylim=c(0,40))
o1<-glm(gpp ~ temp, weight=NULL, family=gaussian)
os1<-segmented(o1, seg.Z=~temp, psi=15, control=seg.control(n.boot=0, 
display=T, it.max=5))
plot(os1, add=TRUE, res=TRUE, se=FALSE, show.gap=TRUE, linkinv = FALSE,
res.col=1, rev.sgn=FALSE, const=0)
summary(os1)


And the most surprising fact is that it works for some of my data, eg:

temp	gpp
5	5.08050857592085
10	9.50809597873546
15	21.0206415558052
20	21.5340216521042
25	22.8455243983385
30	17.6106786978697


but not for the others, that fit within similar range (in what case I tired to
change the psi value but it didn't help), eg:

temp	gpp
5	10.1494724447878
10	9.64730588470101
15	19.3439579009423
20	20.6756229089911
25	13.7902544619339
30	21.9355758560751


or

temp	gpp
5	8.64380785577685
10	9.47992535226006
15	16.7556554476544
20	14.5189937476639
25	20.6874556832793
30	17.5509059595314


I saw post with similar questons but none of them had the answer I am looking
for.
Would there be anyone that could help me with this?


Thanks a lot for your time and help.


Best regards,

Szymon

dear Szymon,

what do you mean

"it does not work for others.. that fit within similar range"?

Each dataset has its own features and breakpoint estimation is not as 
simple as estimation of linear models even if your data "fit within 
similar range".

I will contact you out of the list for details,

best,
vito




Il 08/05/2012 16.44, Szymon Biskup ha scritto:
> Hi everyone,
>
> while trying to use 'segmented' (R i386 2.15.0 for Windows 32bit
OS) to determine the breakpoint I got stuck with an error message and I
can't find solution. It is connected with psi value, and the error says:
>
>
>
> Error in seg.glm.fit(y, XREG, Z, PSI, weights, offs, opz) :
>    (Some) estimated psi out of its range
>
>
>
> This is the code I am using:
>
> library("segmented")
> curva<-read.table("lamintr1.txt", header=T)
> attach(curva)
> fit.glm<-glm(gpp~temp, weight=NULL, family=gaussian)
> plot(temp,gpp,xlab=expression("temp"),
> ylab="gpp",pch=15,cex=0.8,xlim=c(0,50), ylim=c(0,40))
> o1<-glm(gpp ~ temp, weight=NULL, family=gaussian)
> os1<-segmented(o1, seg.Z=~temp, psi=15, control=seg.control(n.boot=0,
> display=T, it.max=5))
> plot(os1, add=TRUE, res=TRUE, se=FALSE, show.gap=TRUE, linkinv = FALSE,
> res.col=1, rev.sgn=FALSE, const=0)
> summary(os1)
>
>
> And the most surprising fact is that it works for some of my data, eg:
>
> temp	gpp
> 5	5.08050857592085
> 10	9.50809597873546
> 15	21.0206415558052
> 20	21.5340216521042
> 25	22.8455243983385
> 30	17.6106786978697
>
>
> but not for the others, that fit within similar range (in what case I tired
to change the psi value but it didn't help), eg:
>
> temp	gpp
> 5	10.1494724447878
> 10	9.64730588470101
> 15	19.3439579009423
> 20	20.6756229089911
> 25	13.7902544619339
> 30	21.9355758560751
>
>
> or
>
> temp	gpp
> 5	8.64380785577685
> 10	9.47992535226006
> 15	16.7556554476544
> 20	14.5189937476639
> 25	20.6874556832793
> 30	17.5509059595314
>
>
> I saw post with similar questons but none of them had the answer I am
looking for.
> Would there be anyone that could help me with this?
>
>
> Thanks a lot for your time and help.
>
>
> Best regards,
>
> Szymon
>
> ______________________________________________
> R-help at 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.
>
-- 
===================================Vito M.R. Muggeo
Dip.to Sc Statist e Matem `Vianelli'
Universit? di Palermo
viale delle Scienze, edificio 13
90128 Palermo - ITALY
tel: 091 23895240
fax: 091 485726
http://dssm.unipa.it/vmuggeo