R help - May 2007 - Function to convert categorical variable in numerical

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?model.matrix
?contr.treatment

Whether this makes sense for PCA is another matter: princomp() contains a 
test to stop this happening automatically with a formula argument. One 
problem is the result depends on just how you do the transformation.


On Thu, 24 May 2007, J.Andr?s Mart?nez wrote:
> Hello everybody,
>
> I am a new R user. At current moment I need to do a Principal Components
> Analysis with a table who contain mixed variables (categorical and
> numerical). There is some function available in R for transform these
> variables?
>
> For example: I need transform the categorical variable X who has 3 classes
> in 2 numerical variables with 0s and 1s.
>
> Thank you very much,
> J. Andres
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at stat.math.ethz.ch 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,                  ripley at 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

Hi J. Andres,

You are probably better off using the ade4 package, which has two functions
that will do exactly what you want, i.e. a PCA using mixed quantitative and
categorical variables:

## You will need to download ade4 first
library(ade4)
?dudi.hillsmith
?dudi.mix

Regards,
Mark Difford.



J.Andr?s Mart?nez wrote:
> 
> Hello everybody,
> 
> I am a new R user. At current moment I need to do a Principal Components
> Analysis with a table who contain mixed variables (categorical and
> numerical). There is some function available in R for transform these
> variables?
> 
> For example: I need transform the categorical variable X who has 3 classes
> in 2 numerical variables with 0s and 1s.
> 
> Thank you very much,
> J. Andres
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch 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.
> 
> 
-- 
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