R help - Apr 2023 - on lexical scoping....

On Tue, Apr 4, 2023 at 7:26?PM akshay kulkarni <akshay_e4 at 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
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

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.sarkar at gmail.com>
Sent: Tuesday, April 4, 2023 7:51 PM
To: akshay kulkarni <akshay_e4 at hotmail.com>
Cc: R help Mailing list <r-help at r-project.org>
Subject: Re: [R] on lexical scoping....



On Tue, Apr 4, 2023 at 7:26?PM akshay kulkarni <akshay_e4 at
hotmail.com<mailto:akshay_e4 at 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

        [[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org<mailto:R-help at r-project.org> mailing list -- To
UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

	[[alternative HTML version deleted]]