On 06-Mar-09 09:25:26, Prof Brian Ripley wrote:
> You might want to look into correspondence analysis, which has several
> variants of PCA designed for categorical data.
In particular, have a look at the results of
RSiteSearch("correspondence")
Ted.
> On Fri, 6 Mar 2009, Galanidis Alexandros wrote:
>
>> Hi all,
>>
>> I' m trying to figure out if it is appropriate to do a PCA having only
>> categorical data (not ordinal). I have only find the following quote:
>>
>> One method to find such relationships is to select appropriate
>> variables and
>> to view the data using a method like Principle Components Analysis
>> (PCA) [4].
>> This approach gives us a clear picture of the data using KL-plot of
>> the PCA.
>> However, the method is not settled for the data including categorical
>> data.
>> [http://hp.vector.co.jp/authors/VA038807/personal/covEigGiniRep17.pdf]
>>
>> but I'm still not sure if it WRONG to do so.
>
> Since normally categorical data is taken to be binomial or Poisson
> distributed, the variance varies with the mean and least-squares (the
> basis of PCA) is then sub-optimal. Correspondence analysis takes that
> into account (at least to some extent).
>
>> Any opinion or reference would be very helpful
>
> There is a basic introduction in MASS4, with references to more
> comprehensive accounts.
>
>> thanks
>>
>> ______________________________________________
>> 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.
>>
>
> --
> Brian D. Ripley, rip...@stats.ox.ac.uk
> Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
> University of Oxford, Tel: +44 1865 272861 (self)
> 1 South Parks Road, +44 1865 272866 (PA)
> Oxford OX1 3TG, UK Fax: +44 1865 272595
>
> ______________________________________________
> 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.
--------------------------------------------------------------------
E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 06-Mar-09 Time: 09:46:15
------------------------------ XFMail ------------------------------
______________________________________________
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.
