[R] using names() as a variable in a formula

[Duncan Murdoch]

On Wed, 18 Feb 2004 15:44:59 -0500, "femke" <femke at geog.umd.edu> wrote
>> v<-variogram(A1~1,loc=~x+y, dataC)


What package is variogram in?  The one in spatial takes different
args.

>> v<-variogram(names(dataC[3])~1,loc=~x+y, dataC)

Doing this sort of thing is tricky.  Your names(dataC[3]) is a
character string; you want something there that would be interpreted
as a name instead.  However, as.name(names(dataC[3])) isn't enough.

I think you need to build up the formula using fairly low level stuff,
something like this:

   formula <- as.call(list(as.name('~'), as.name(names(dataC[3])),
quote(1)))

and then do

  variogram(formula, ....)

but a formula constructed this way doesn't work in lm(), so it may not
work in variogram either.

Duncan Murdoch