[R] Partial matching list elements in R 4.0

[David Winsemius]

There is a modifyList function in pkg utils that is used extensively in 
the code for lattice graphics:


  var$options <- modifyList(var$options, list( misc=list(abc = "123"), 
mi= list(something    = 13))
                                              )

#-------------------

 > var
$options
$options$mi
$options$mi$something
[1] 13


$options$misc
$options$misc$abc
[1] "123"

On 5/26/20 11:31 AM, Bert Gunter wrote:
> I can't answer your question (about your R programming skills) but the
> behavior you complain about is as documented. In particular:
>
> "Thus the default behaviour is to use partial matching only when extracting
> from recursive objects (except environments) by $. Even in that case,
> warnings can be switched on by options
> <http://127.0.0.1:39592/help/library/base/help/options>(warnPartialMatchDollar
> = TRUE)."
>
> So the solution is not to use $ for list extraction/replacement. Though
> convenient, it is prone to such issues. Instead, the following works (as
> does your suggested solution, of course):
>
>> var <- list()
>> var[["options"]][["misc"]][["abc"]] <- "123"
>> var[["options"]][["mi"]][["something"]] <- 13
>> var
> $options
> $options$misc
> $options$misc$abc
> [1] "123"
>
>
> $options$mi
> $options$mi$something
> [1] 13
>
> Bert Gunter
>
> "The trouble with having an open mind is that people keep coming along and
> sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
>
> On Tue, May 26, 2020 at 10:45 AM John Harrold <john.m.harrold using gmail.com>
> wrote:
>
>> Hello,
>>
>>
>> I'm testing some code in R 4.0, and I'm having an issue with the following"
>>
>> # -------------
>> rm(list=ls())
>> graphics.off()
>> #load("/tmp/post.RData")
>> var = list();
>> # If I uncomment this it fixes things:
>> # var$options = list(mi   = list(),
>> #                    misc = list())
>> #
>> var$options$misc$abc = "123"
>> var$options$mi$something    = 13
>> #------------
>>
>> This is a stripped down example but it exhibits the issue I"m having.
>> Basically when I create the list element var$options$mi the contents of
>> var$options$misc move over to var$options$mi. And what was in
>> var$options$misc become NULL:
>>
>> So now var$options looks like:
>>
>> var$options
>> $misc
>> $misc$abc
>> NULL
>>
>> $mi
>> $mi$abc
>> [1] "123"
>> $mi$something
>> [1] 13
>>
>> This worked (still works) in R 3.5.1. I understand partial matching, but is
>> this normal lists moving over to elements like this? I can uncomment the
>> text mentioned in the example and it seems to fix it, but I'm wondering if
>> this is a bug or just my poor programming coming back to bite me.
>>
>> I've included my sessionInfo() at the bottom.
>>
>> Thanks
>> John
>> :wq
>>
>>
>> sessionInfo()
>>
>> R version 4.0.0 (2020-04-24)
>>
>> Platform: x86_64-apple-darwin17.0 (64-bit)
>>
>> Running under: macOS Mojave 10.14.5
>>
>>
>> Matrix products: default
>>
>> BLAS:
>> /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRblas.dylib
>>
>> LAPACK:
>> /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRlapack.dylib
>>
>>
>> locale:
>>
>> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
>>
>>
>> attached base packages:
>>
>> [1] stats     graphics  grDevices utils     datasets  methods   base
>>
>>
>> other attached packages:
>>
>> [1] gdata_2.18.0  ggplot2_3.3.0 deSolve_1.28
>>
>>
>> loaded via a namespace (and not attached):
>>
>>   [1] Rcpp_1.0.4.6     gtools_3.8.2     withr_2.2.0      assertthat_0.2.1
>>
>>   [5] dplyr_0.8.5      digest_0.6.25    crayon_1.3.4     grid_4.0.0
>>
>>   [9] R6_2.4.1         lifecycle_0.2.0  gtable_0.3.0     magrittr_1.5
>>
>> [13] scales_1.1.1     pillar_1.4.4     rlang_0.4.6      vctrs_0.3.0
>>
>> [17] ellipsis_0.3.1   glue_1.4.1       purrr_0.3.4      munsell_0.5.0
>>
>> [21] compiler_4.0.0   pkgconfig_2.0.3  colorspace_1.4-1 tidyselect_1.1.0
>>
>> [25] tibble_3.0.1
>>
>>          [[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.
>>
> 	[[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.