[R] Linear Regression ?

[Roland Rau]

Hi,

did you have a look at the manual "An Introduction to R"? 
(http://cran.r-project.org/doc/manuals/R-intro.html).
Chapter "Statistical Models in R" should answer (most of) your questions 
concerning linear regression.

kayj wrote:
> 
> Also each x is a categorical variable with 4 categories so I have to
> introduce  three variables for each x 
> 

If I understood correctly what you mean (-> coding of dummy variables), 
this is not necessary in R. If you variable is a "factor", R does it for 
you automatically. If you are unhappy with the choice of reference 
category,  please check:
?relevel

I hope this helps,
Roland