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 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
>
>
>
>
> ______________________________________________
> R-help@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.
>
--
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@Ugent.be
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