[R] Partial matching list elements in R 4.0

[Bert Gunter]

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
>
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>
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