Sorry this has taken so long to get back to you, I have been out of the office a lot recently.
 
The documentation for read.table suggests that since an as.ordered function exists, that you could just use "ordered" as a column class, but I don't know how well that works in practice.  In general I think it is better to let read.table create regular factors, then change them to ordered factors by hand afterwards.  For regular factors, the default ordering (since order does not matter) is alphabetical by factor level.  This is not usually the correct ordering for ordered factors and read.table has no way of knowing what the proper order should be.  When you change them by hand you can specify the ordering rather than taking the usually wrong default.
 
 

--
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow@intermountainmail.org
(801) 408-8111



 


________________________________

	From: Birgit Lemcke [mailto:birgit.lemcke@systbot.uzh.ch] 
	Sent: Friday, August 24, 2007 2:13 AM
	To: Greg Snow
	Cc: R Hilfe
	Subject: Re: [R] ordered factors in data.frame
	
	
	Thanks a lot Greg for your help. 

	This works fine.

	Normally I use a vector to set the classes for the variables:

	Classe<-cclasses <- c(rep("factor", 14), rep("numeric", 4))
	Table1<-read.table("Name", sep = ";", colClasses = Classe)
	
	
	How can I implement to set colClasses as ordererd factor here.
	
	
	Following works not:
	
	
	Classe<-cclasses <- c(rep("factor", 61), rep("numeric", 14), rep("odered", 10))


	Thanks in advance

	Birgit


	
	
	
	

	Am 23.08.2007 um 21:21 schrieb Greg Snow:


		The attach function only attachs a copy of the data (changes to the data don't show up in the attached copy).  Also you need to tell R what to do with the result of as.ordered (where to save it).

		Try something like:


			table$V3 <- as.ordered(table$V3)


		Or


			table <- transform(table, V3=as.ordered(V3) )


		Hope this helps,

		-- 
		Gregory (Greg) L. Snow Ph.D.
		Statistical Data Center
		Intermountain Healthcare
		greg.snow@intermountainmail.org
		(801) 408-8111




			-----Original Message-----
			From: r-help-bounces@stat.math.ethz.ch 
			[mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Birgit Lemcke
			Sent: Thursday, August 23, 2007 11:28 AM
			To: R Hilfe
			Subject: [R] ordered factors in data.frame

			Hello I need a tiny peace of help. (PPC Mac Os X 10.4.10; R 2.5.1)

			I have a data.frame with numeric and factor variables.
			I would like to convert same of the factors to ordered factors.

			I tried with:

			attach (table)

			as.ordered (V3)

			but this gives me only the V3 Vector as ordred back but in 
			the data.frame (str(Table)) it is still not ordered.

			How can I do that?

			Thanks for your help.

			I am still a beginner.

			Greetings

			Birgit

			Now I would like to
			Birgit Lemcke
			Institut für Systematische Botanik
			Zollikerstrasse 107
			CH-8008 Zürich
			Switzerland
			Ph: +41 (0)44 634 8351
			birgit.lemcke@systbot.uzh.ch






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	Birgit Lemcke
	Institut für Systematische Botanik
	Zollikerstrasse 107
	CH-8008 Zürich
	Switzerland
	Ph: +41 (0)44 634 8351
	birgit.lemcke@systbot.uzh.ch
	 






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