R-alpha: User friendly functions

[Peter Dalgaard BSA]

Kurt Hornik <Kurt.Hornik@ci.tuwien.ac.at> writes:

> > dfr.sel<-select.frame(dfr,age,sex,pain1:pain5)
> 
> > dfr.sub<-subset.frame(dfr,sex==1 && age > 30)
> 
> Something like that would be very nice to have.

I got a working select.frame() during the weekend. Really easy, once you
get the hang of constructions of the type

eval(as.call(subst.expr(c(as.name("c"),expression(...)))))

- with subst.expr() recursively replacing call arguments with
corresponding numbers using match(). As a bonus, it is actually
possible to do stuff like

select.frame(psychometry,seq(scale1.before,scale15.before,2))

and get every *second* variable in the range (skipping "after"
measurements) 

Next: subset.frame() - before I do the obvious: Is there a simple way
of getting R to search a frame *before* the global environment?

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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