Dear Duncan,
THanks for the reply...!
So the takeaway is that define the symbol in the same environment before using
it right!?
Thanking you,
Yours sincerely,
AKSHAY M KULKARNI
________________________________
From: Duncan Murdoch <murdoch.dun...@gmail.com>
Sent: Tuesday, April 4, 2023 8:21 PM
To: akshay kulkarni <akshay...@hotmail.com>; Deepayan Sarkar
<deepayan.sar...@gmail.com>
Cc: R help Mailing list <r-help@r-project.org>
Subject: Re: [R] on lexical scoping....
You can't change the basic way R searches, but you can ask for a
different kind of search. For example, to see if "x" exists, you can use
exists("x")
and it will do the default search, but
exists("x", inherits = FALSE)
will only look in the current environment. The get() function has a
similar argument which returns the value
Unfortunately these functions have overly complicated argument lists
because they are based on functions in S from 30-40 years ago, and it
had very different scoping rules. My advice would be to ignore the
"where" and "frame" arguments, and always use "envir" if you want to say
where to look.
Duncan Murdoch
On 04/04/2023 10:28 a.m., akshay kulkarni wrote:
> Dear Deepayan,
> THanks for the pithy, pointed reply.
>
> But isn't it risky? Can I somehow get a warning when x is not defined in the
> global environment but takes on a value from one of the loaded packages? any
> packages for that?
>
> THanking you,
> Yours sincerely,
> AKSHAY M KULKARNI
> ________________________________
> From: Deepayan Sarkar <deepayan.sar...@gmail.com>
> Sent: Tuesday, April 4, 2023 7:51 PM
> To: akshay kulkarni <akshay...@hotmail.com>
> Cc: R help Mailing list <r-help@r-project.org>
> Subject: Re: [R] on lexical scoping....
>
>
>
> On Tue, Apr 4, 2023 at 7:26 PM akshay kulkarni
> <akshay...@hotmail.com<mailto:akshay...@hotmail.com>> wrote:
> Dear Members,
> I have the following code typed at the console
> prompt:
>
> y <- x*10
>
> X has not been defined and the above code throws an object not found error.
> That is, the global environment does not contain x.
>
> That is not the correct interpretation of the error. R will happily evaluate
>
> y <- pi*10
>
> even if the global environment does not contain pi. The "environments" where
> R will look is given by
>
> search()
>
> If you manage to find a package that defines 'x' (and exports it), attaching
> it will put the package on the search path, and then your call will indeed no
> longer give an error.
>
> -Deepayan
>
> Why doesn't it look further in the environment stack, like that of packages?
> There are thousands of packages that contain the variable named x. Of
> course, that happens if the above code is in a function (or does it?).
>
> What concept of R is at work in this dichotomy?
>
> THanking you,
> Yours sincerely,
> AKSHAY M KULKARNI
>
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>
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>
> ______________________________________________
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