[R] ordinal variables

[S Ellison]

If you set them a problem that has them doing the same sort of thing
five times and compare the time it takes with code pasted from an editor
(eg Tinn-R) and the time it takes via menius, you may have more luck
convincing them.

A command line sequence is harder than menus the first two times but
easier for any n iterations thereafter.

Steve ellison

>>> Iasonas Lamprianou <lamprianou at yahoo.com> 03/06/2010 14:51 >>>
Thank you Joris,
I'll have a look into the commands you sent me. They look convincing. I
hope my students will also see them in a positive way (although I can
force them to pretend that they have a positive attitude)!

Dr. Iasonas Lamprianou





Assistant Professor (Educational Research and Evaluation)

Department of Education Sciences

European University-Cyprus

P.O. Box 22006

1516 Nicosia

Cyprus 

Tel.: +357-22-713178

Fax: +357-22-590539





Honorary Research Fellow

Department of Education

The University of Manchester

Oxford Road, Manchester M13 9PL, UK

Tel. 0044  161 275 3485

iasonas.lamprianou at manchester.ac.uk 

--- On Thu, 3/6/10, Joris Meys <jorismeys at gmail.com> wrote:

From: Joris Meys <jorismeys at gmail.com>
Subject: Re: [R] ordinal variables
To: "Iasonas Lamprianou" <lamprianou at yahoo.com>
Cc: r-help at r-project.org 
Date: Thursday, 3 June, 2010, 14:35

see ?factor and ?as.factor. On ordered factors you can technically do a
spearman without problem, apart from the fact that a spearman test by
definition cannot give exact p-values with ties present.

x <- sample(c("a","b","c","d","e"),100,replace=T)

y <- sample(c("a","b","c","d","e"),100,replace=T)

x.ordered <- factor(x,levels=c("e","b","a","d","c"),ordered=T)

x.ordered
y.ordered <- factor(y,levels=c("e","b","a","d","c"),ordered=T)
y.ordered

cor.test(x.ordered,y.ordered,method="spearman")

require(pspearman)

spearman.test(x.ordered,y.ordered)

R commander has some menu options to deal with factors. R commander
also provides a scripting window. Please do your students a favor, and
show them how to use those commands. 


Cheers
Joris


On Thu, Jun 3, 2010 at 2:25 PM, Iasonas Lamprianou
<lamprianou at yahoo.com> wrote:

Dear colleagues,



I teach statistics using SPSS. I want to use R instead. I hit on one
problem and I need some quick advice. When I want to work with ordinal
variables, in SPSS I can compute the median or create a barchart or
compute a spearman correlation with no problems. In R, if I "read" the
ordinal variable as numeric, then I cannot do a barplot because I miss
the category names. If I read the variables as characters, then I cannot
run a spearman. How can I read a variable as numeric, still have the
chance to assign value labels, and be able to get table of frequencies
etc? I want to be able to do all these things in R commander. My
students will probable be scared away if I try anything else other than
R commander (just writing commands will not make them happy).




I hope I am not asking for too much. Hopefully there is a way









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-- 
Joris Meys
Statistical Consultant

Ghent University
Faculty of Bioscience Engineering 
Department of Applied mathematics, biometrics and process control


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