Using with() to avoid $ ?
Yes, variables in the formula should be handled by nse with the data argument. Got it -- thanks. But still ... can with() be used to handle those and/or any other variables in foo that appear as arguments. I see no problems in doing so, but ... ? Bert (But see inline below)
On Oct 23, 2016 7:24 PM, "Jeff Newmiller" <jdnewmil at dcn.davis.ca.us> wrote:
No. And I don't know why you are conflating the treatment of variables in
the formula with treatment of variables passed as other arguments. It is sort of like thinking the x symbols in foo$x[ x < 0 ] refer to the same data. In my query they explicitly do, though. Nevertheless your response was apropos.
foo$y ~ foo$x1 + foo$x2 + foo$x3 is not preferable, and given the
availability of a data argument such redundancy is unnecessary. NSE is already in use for the formula. It is not (necessarily) in use for the other arguments, so you just have to learn which arguments are being handled with NSE by any particular function and which are not... good docs would be the preferred avenue but recognizing the error message that arises when you fail to specify foo$ for the non-formula arguments gets me by if the docs are unclear.
However, it is dangerous to apply NSE tricks recursively, so piling
"with" on top of the existing formula eval-with-data is only likely to confuse the evaluation context even more. This is what I'm not sure of. Can you give an example of when such confusion would occur?
-- Sent from my phone. Please excuse my brevity. On October 23, 2016 9:18:17 AM PDT, Bert Gunter <bgunter.4567 at gmail.com>
wrote:
As has been noted oftimes on this list
f( y ~ x1 + x2 + x3 + ... , data = foo, ...)
is much preferable to
f( foo$y ~ foo$x1 + foo$x2 + foo$x3 + ..., ...)
(with no data argument), using nse = non-standard evaluation to set the
environment for formula evaluation. However, as queries here recently
demonstrate, the formula variables (y, x1, x2, x3, ...) or other
variables
in foo are also sometimes needed as further arguments of f, and these
have
to be explicitly and tediously given as foo$whatever or equivalent
indexing.
So my question is, can/should with() be used instead in the form
with(foo, f( y ~ x1 + x2 + x3 + ... , data = foo, ...)) with no
explicit
$ or indexing in ... variables?
or even
with(foo, f( y ~ x1 + x2 + x3 + ... , ...))
with no data argument for nse or indexing, though this seems to me
questionable in that it may affect the formula's environment
differently.(??)
Please correct any misstatements of fact in the above as well as
clarifying
anything else I seem confused about.
Many thanks.
Bert
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