Maybe I'm missing something (a common occurrence), but doesn't this
solution beg the question that Peter's example answered: his tree model
indicates that, with respect to the response variable, the factors are not
ordered.
__________________________________________________
Don McKenzie, Fire and Landscape Ecologist
Fire and Environmental Research Applications (FERA)
Seattle Forestry Sciences Lab, USDA Forest Service
donaldmckenzie@fs.fed.us
dmck@u.washington.edu
(206)732-7824; fax (206)732-7801
__________________________________________________
On Thu, 30 Jan 2003, John Fox wrote:
> Dear Peter,
>
> There's no reason not to use numbers to represent the factor -- any numbers
> in the correct order will do, such as integers 1 through 8. Splits will be
> between adjacent numbers and hence will preserve the order of the factor.
>
> I hope that this helps,
> John
>
> At 10:57 AM 1/30/2003 -0500, you wrote:
> >Hello
> >
> >I am running S-Plus 6 on a Windows machine.
> >
> >I am trying to fit a classification tree with independent variables
> >that are ordinal. However the result does not take the ordinalaity of
> >the variables into account. e.g., one variable has levels A through H.
> >I have made this an ordinal factor in the data window. But the tree
> >gives splits such as
> >
> >AC BDEFGH
> >
> >I had thought of perhaps numericizing the scale, but this doesn't seem
> >ideal to me. Is there a better solution?
> >
> >Thanks in advance
> >
> >Peter
> >
> >
> >
> >Peter L. Flom, PhD
> >Assistant Director, Statistics and Data Analysis Core
> >Center for Drug Use and HIV Research
> >National Development and Research Institutes
> >71 W. 23rd St
> >New York, NY 10010
> >(212) 845-4485 (voice)
> >(917) 438-0894 (fax)
> >
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> -----------------------------------------------------
> John Fox
> Department of Sociology
> McMaster University
> Hamilton, Ontario, Canada L8S 4M4
> email: jfox@mcmaster.ca
> phone: 905-525-9140x23604
> web: www.socsci.mcmaster.ca/jfox
> -----------------------------------------------------
>
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