[R] ordinal variables
S Ellison
S.Ellison at lgc.co.uk
Thu Jun 3 16:44:26 CEST 2010
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
Coupure Links 653
B-9000 Gent
tel : +32 9 264 59 87
Joris.Meys at Ugent.be
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