Soren,

It sounds like you are new to R so I will refer you to some packages that I think some people would find more user friendly as beginners.  

Zelig is excellent.  You could run a series of logistic regressions coding your dependent variables as follows (a versus b, a versus c, b versus c)  

See the website below

http://gking.harvard.edu/zelig/docs/index.html

Alternatively you could try Rattle

See the website below

http://rattle.togaware.com/rattle-features.html

Or you could try Rcmder

HTH Paul


> soeren.vogel@eawag.ch wrote:
> 
> Hi,
> 
> y is nominal (3 categories), x1 to 3 is scale. What I want is a  
> regression, showing the probability to fall in one of the three  
> categories of y according to the x. How can I perform such a  
> regression in R?
> 
> Thanks for your help
> 
> Sören
> 
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