[R] with vs. attach

Spencer Graves spencer.graves at effectivedefense.org
Fri May 6 02:12:48 CEST 2016

I want a function to evaluate one argument
in the environment of a data.frame supplied
as another argument.  "attach" works for
this, but "with" does not.  Is there a way
to make "with" work?  I'd rather not attach
the data.frame.

With the following two functions "eval.w.attach"
works but "eval.w.with" fails:

dat <- data.frame(a=1:2)
eval.w.attach <- function(x, dat){
   X <- x

eval.w.with <- function(x, dat){
   with(dat, x)

eval.w.attach(a/2, dat) # returns c(.5, 1)

eval.w.with(a/2, dat) # Error ... 'a' not found

Thanks, Spencer Graves

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