On 01/10/2010 12:00 PM, Joris Meys wrote:
Dear,
I'm following the r tag on stackoverflow.com, and couldn't but notice
there are quite some questions popping up that deal with scoping in
relation to custom functions. I grinded my teeth on it already, and I
have absolutely no clue what goes wrong. The general pattern is as
follows :
I think each of the reports is really a separate bug, mostly in the
implementation of "some_function". As far as I could see, only the last one
|y<- new.env()
with(y, x<- 1)
f<- function(env,z) {
with(env, x+z)
}
f(y,z=1)
|
involves base R functions, and there I think the problem is with your
reading of the documentation, not with the function. The documentation
may suggest that should work by saying "The environment has the caller's
environment as its parent", but there's no way it possibly could.
Environments only have one parent. If you read carefully you'll see that
this is documented correctly in "(Note: if ‘data’ is already an
environment then this is used with its existing parent.)"
Duncan Murdoch
ff<- function(x){
y<- some_value
some_function(y)
}
> ff(x)
Error in eval(expr, envir, enclos) : object 'y' not found
I tried to report this as a bug earlier, but got the message I used
the wrong channel. I also don't know how to formalize it into a bug
report on the report site. That's why I bring it to your attention
this way, and want to ask you whether this is by design and we're all
doing something wrong, whether these are problems within certain
packages/situations, ...
I solve these problems now by adding an environment to my global
environment, and delete it after the function finished running. But
this can't be the correct way.
The problem is described here :
http://stackoverflow.com/questions/3840769/scoping-and-functions-in-r-2-11-1-whats-going-wrong
Links to different reports, all having that same pattern but with
different functions :
http://stackoverflow.com/questions/3742415/r-statistical-scoping-error-using-transformby-part-of-the-doby-package
http://stackoverflow.com/questions/3768417/how-to-use-acast-reshape2-within-a-function-in-r
http://stackoverflow.com/questions/3661500/why-cant-i-pass-a-dataset-to-a-function
http://stackoverflow.com/questions/3574858/values-not-being-copied-to-the-next-local-environment
http://stackoverflow.com/questions/2646402/using-functions-and-environments
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