Dear Nick, dear H�kon,
thank you very much for your helpful replies.
The method H�kon suggested works, and it might also work to define instead
another category of the variable as omitted.
However, Nick, when I have another base category then r2==15 the problem
with the dropped variables disappears: they are not any more dropped and
have good explanatory power, as expected. Though I see your point I feel
that the division of labour, as you call it so nicely, between xi and the
reg command is not really helpful. At least it caused some headaches to me.
Dankwart
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
