[R] error in exists.....

[Bert Gunter]

There is no substitute for experience/knowledge; nor any universally
optimal strategy for debugging. But using the debugging tools that R
provides -- ?debug, ?traceback, ?recover (e.g. in the form of
options(error = utils::recover) ) -- should always be the first goto
(or maybe the second after carefully re-reading relevant Help docs).
However, the debugging tools would not have helped here afaics.

-- Bert

On Tue, Dec 27, 2022 at 10:22 AM akshay kulkarni <akshay_e4 using hotmail.com> wrote:
>
> Dear Bert,
>                    Yeah, it's working....Sometimes (only sometimes) I feel that I am troubling this list with very simple questions the answer to which I always happen to find myself a little after...any solutions for that (you seem to be an omniscient person)!?
>
> Thanking you,
> Yours sincerely,
> AKSHAY M KULKARNI
> ________________________________
> From: Bert Gunter <bgunter.4567 using gmail.com>
> Sent: Tuesday, December 27, 2022 11:39 PM
> To: akshay kulkarni <akshay_e4 using hotmail.com>
> Cc: Sarah Goslee <sarah.goslee using gmail.com>; R help Mailing list <r-help using r-project.org>
> Subject: Re: [R] error in exists.....
>
> You are confused about the list hierarchy. Perhaps this will explain:
> > i <- 1
> >  E <- new.env()
> >   E$L <- list()  ## L is an empty list in E
> >   i <- 1
> >    E$L[[i]]$T1A1 <- Sys.time()
> Error in `*tmp*`[[i]] : subscript out of bounds
> ## L is empty, so L[[1]] does not exist; is not a list;
> ## cannot have a value assigned to a component
> ## The following works:
> ## Create an empty list as a sublist of L
> >  E$L[[1]] <- list()
> ## Now create and assign to a component of the empty list
> >  E$L[[i]]$T1A1 <- Sys.time()
> > E$L ## a list
> [[1]]  ## whose first component is a list
> [[1]]$T1A1 ## T1A1 named component of L[[1]]
> [1] "2022-12-27 10:00:10 PST"
>
> ergo, no conundra... (assuming I've understood you correctly)
>
> Cheers,
> Bert
>
> On Tue, Dec 27, 2022 at 9:57 AM akshay kulkarni <akshay_e4 using hotmail.com> wrote:
> >
> > Dear Sarah,
> >                      I had this also before the assignment of Sys.time():
> >
> > >     E$L[[i]] <- i
> >
> > After assignment of Sys.time():
> >
> > > E$L
> > [[1]]
> > [[1]][[1]]
> > [1] 1
> >
> > [[1]]$T1A1
> > [1] "2022-12-27 22:40:02 IST"
> >
> > regrets for not sharing this ......Can you reproduce it now?
> >
> > Thanking you,
> > Yours sincerely,
> > AKSHAY M KULKARNI
> > ________________________________
> > From: Sarah Goslee <sarah.goslee using gmail.com>
> > Sent: Tuesday, December 27, 2022 11:20 PM
> > To: akshay kulkarni <akshay_e4 using hotmail.com>
> > Cc: R help Mailing list <r-help using r-project.org>
> > Subject: Re: [R] error in exists.....
> >
> > Hi,
> >
> > I can't create the desired object using the code you provided, but if
> > I create it in two steps so that E$L[[i]]$T1A1 does exist, exist()
> > returns TRUE.
> >
> > E <- new.env()
> > E$L <- list()
> > i <- 1
> > E$L[[i]]$T1A1 <- Sys.time()
> >
> > # returns: Error in `*tmp*`[[i]] : subscript out of bounds
> >
> > E$L[[i]] <- list()
> > E$L[[i]]$T1A1 <- Sys.time()
> >
> >
> > exists("T1A1", where = E$L[[i]])
> > # returns: [1] TRUE
> >
> >
> > > str(E$L)
> > List of 1
> >  $ :List of 1
> >   ..$ T1A1: POSIXct[1:1], format: "2022-12-27 12:47:26"
> >
> > Sarah
> >
> > On Tue, Dec 27, 2022 at 12:36 PM akshay kulkarni <akshay_e4 using hotmail.com> wrote:
> > >
> > > Dear members,
> > >                              I have the following code:
> > > >  E <- new.env()
> > > >  E$L <- list()
> > > >  i <- 1
> > > >   E$L[[i]]$T1A1 <- Sys.time()
> > > > exists("T1A1", where = E$L[[i]])
> > > Error in list2env(list(1, T1A1 = 1672161002.38743), NULL, <environment>) :
> > >   attempt to use zero-length variable name
> > >
> > > I want the output of the exists() function to be TRUE. In any case:
> > >
> > > > E$L[[1]]$T1A1
> > > [1] "2022-12-27 22:40:02 IST"
> > >
> > > Please help me solve this conundrum....
> > >
> > > Thanking you,
> > > Yours sincerely,
> > > AKSHAY M KULKARNI
> > >
> > >
> > >         [[alternative HTML version deleted]]
> > >
> > > ______________________________________________
> > > R-help using 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.
> >
> >
> >
> > --
> > Sarah Goslee (she/her)
> > http://www.numberwright.com
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help using 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.