R help - Jun 2012 - Finding multiple breakpoints - 'segmented' ?

Hello,

I'm attempting to find multiple breakpoints in an association of my
response variable (R.AUC) with two explanatory variables ('s.size' and
'bedekking'). The association between 's.size' and
'R.AUC' shows a
plateau, but the value when this plateau is reached is differs for
different values of 'bedekking'.

Initially I thought these different values could be assessed by the
'segmented' function in the package of the same name, but this only
seems to give one value of a breakpoint for each explanatory variable.
A similar issue was treated in the following message from 2006:
https://stat.ethz.ch/pipermail/r-help/2006-January/086446.html

Does anybody know whether there are any packages that do have a
function for this? Or might it be a possibility to split up the data
per value of 'bedekking' and then do the segmented function?

dear Peter,
Currently segmented handles multiple breakpoints for several variables 
(the limit discussed in the msg 2006 has been fixed..).

However you are looking for a somewhat complicated model where the 
breakpoint of the relationship 's.size' and 'R.AUC' depends on
another
covariate 'bedekking'. Namely it is an interaction in the breakpoint 
parameter (rather then in a linear parameter).

Currently segmented is not able to deal with these interactions, and 
splitting up the data into two or three groups according the values of 
bedekking could be a feasible alternative.

Hope this helps you,

vito




Il 01/06/2012 11.35, Peter Hoitinga ha scritto:
> Hello,
>
> I'm attempting to find multiple breakpoints in an association of my
> response variable (R.AUC) with two explanatory variables ('s.size'
and
> 'bedekking'). The association between 's.size' and
'R.AUC' shows a
> plateau, but the value when this plateau is reached is differs for
> different values of 'bedekking'.
>
> Initially I thought these different values could be assessed by the
> 'segmented' function in the package of the same name, but this only
> seems to give one value of a breakpoint for each explanatory variable.
> A similar issue was treated in the following message from 2006:
> https://stat.ethz.ch/pipermail/r-help/2006-January/086446.html
>
> Does anybody know whether there are any packages that do have a
> function for this? Or might it be a possibility to split up the data
> per value of 'bedekking' and then do the segmented function?
>
> ______________________________________________
> 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