On 06/11/2015 8:20 AM, Therneau, Terry M., Ph.D. wrote:
Duncan,
That's helpful. Two follow-up questions:
1. Where would I have found this information? I had looked at eval and
model.frame.
I think the best description is Luke's article on namespaces, "Name
space management for R". Luke Tierney, R News, 3(1):2-6, June 2003.
There's a link to it from the "Technical papers" section of the HTML
help index. There's also a short description of this in the R Language
Definition manual in the "Search path" section 3.5.4.
2. What stops the following code from falling down the same rabbit hole?
Shouldn't it
find base::cos first?
library(survival)
cos <- lung
coxph(Surv(time, status) ~ age, data=cos)
If that code is in a function anywhere (package or not), cos will be a
local variable created there in the evaluation environment created when
you evaluate the function. If you execute it at the command line,
you'll create a variable called "cos" in the global environment. Local
variables come ahead of the 3 places I listed. (This is why Luke's
article is good: it doesn't oversimplify.)
There's one other twist. Even with cos being a local variable,
cos(theta) would find base::cos, because the evaluator knows it is
looking for a function (since it's a function call) and will skip over
the local dataframe named cos.
Duncan Murdoch
Terry T.
On 11/06/2015 07:51 AM, Duncan Murdoch wrote:
On 06/11/2015 7:36 AM, Therneau, Terry M., Ph.D. wrote:
I am currently puzzled by a seach path behavior. I have a library of a dozen
routines
getlabs(), getssn(), getecg(), ... that interface to local repositories and
pull back
patient information. All have a the first 6 arguments in common, and
immediately call a
second routine to do initial processing of these 6. The functions "joe" and
"fred" below
capture the relevant portion of them.
My puzzle is this: the last test in the "test" file works fine if these
routines are
sourced and executed at the command line, it fails if the routines are bundled
up and
loaded as a library. That test is motivated by a user who called his data set
"t", and
ended up with a match to base:::t instead of his data, resulting in a strange
error
message out of model.frame --- you can always count on the users! (There are
a few
hundred.)
I'm attempting to be careful with envr and enclos arguments -- how does
base end up
earlier in the search path? Perhaps this is clearly stated in the docs and
just not
clear to me? A working solution to the dilemma is of course more than welcome.
I haven't followed through all the details in fred(), but I can answer the last
question.
In package code, the search order is:
- the package environment
- the imports to the package (with base being an implicit import)
- the global environment and the rest of the search list.
In code sourced to the global environment, only the third of these is searched.
Since
base is in the second one, it is found first in the package version.
Duncan Murdoch
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