[Rd] Odd behaviour in within.list() when deleting 2+ variables

[Martin Maechler]

>>>>> "PD" == Peter Dalgaard <pdalgd at gmail.com>
>>>>>     on Mon, 26 Jun 2017 20:12:38 +0200 writes:

    >> On 26 Jun 2017, at 19:04 , Martin Maechler
    >> <maechler at stat.math.ethz.ch> wrote:
    >> 
    >>>>>>> peter dalgaard <pdalgd at gmail.com> on Mon, 26 Jun
    >>>>>>> 2017 13:43:28 +0200 writes:
    >> 
    >>> This seems to be due to changes made by Martin Maechler
    >>> in 2008. Presumably this fixed something, but it escapes
    >>> my memory.
    >> 
    >> Yes: The change set (svn -c46441) also contains the
    >> following NEWS entry
    >> 
    >> BUG FIXES
    >> 
    >> o within(<dataframe>, { ... }) now also works when '...'
    >> removes more than one column.
    >> 

    > The odd thing is that the assign-NULL technique used for
    > removing a single column, NOW also seems to work for
    > several columns in a data frame, so I wonder what the
    > bug was back then...

It did not work back then:  We have had lots of improvements in
 [.data.frame in these almost 9 years.

Indeed, the fix I've committed reverts almost to the previous
first version of  within.data.frame  (which is from Peter
Dalgaard, for those who don't know).

Martin


    >>> However, it seems to have broken the equivalence between
    >>> within.list and within.data.frame, so now
    >> 
    >>> within.list <- within.data.frame
    >> 
    >>> does not suffice.
    >> 
    >> There have been many improvements since then, so maybe we
    >> can change the code so that the above will work again.
    >> 
    >> Another problem seems that we had no tests of
    >> within.list() anywhere... so we will have them now.
    >> 
    >> I've hade an idea that seems to work and even simplify
    >> the code....  will get back to the issue later in the
    >> evening.
    >> 
    >> Martin
    >> 
    >> 
    >>> The crux of the matter seems to be that both the
    >>> following constructions work for data frames
    >> 
    >>>> aq <- head(airquality) names(aq)
    >>> [1] "Ozone" "Solar.R" "Wind" "Temp" "Month" "Day"
    >>>> aq[c("Wind","Temp")] <- NULL aq
    >>> Ozone Solar.R Month Day 1 41 190 5 1 2 36 118 5 2 3 12
    >>> 149 5 3 4 18 313 5 4 5 NA NA 5 5 6 28 NA 5 6
    >>>> aq <- head(airquality) aq[c("Wind","Temp")] <-
    >>>> vector("list",2) aq
    >>> Ozone Solar.R Month Day 1 41 190 5 1 2 36 118 5 2 3 12
    >>> 149 5 3 4 18 313 5 4 5 NA NA 5 5 6 28 NA 5 6
    >> 
    >>> However, for lists they differ:
    >> 
    >>>> aq <- as.list(head(airquality)) aq[c("Wind","Temp")] <-
    >>>> vector("list",2) aq
    >>> $Ozone [1] 41 36 12 18 NA 28
    >> 
    >>> $Solar.R [1] 190 118 149 313 NA NA
    >> 
    >>> $Wind NULL
    >> 
    >>> $Temp NULL
    >> 
    >>> $Month [1] 5 5 5 5 5 5
    >> 
    >>> $Day [1] 1 2 3 4 5 6
    >> 
    >>>> aq <- as.list(head(airquality)) aq[c("Wind","Temp")] <-
    >>>> NULL aq
    >>> $Ozone [1] 41 36 12 18 NA 28
    >> 
    >>> $Solar.R [1] 190 118 149 313 NA NA
    >> 
    >>> $Month [1] 5 5 5 5 5 5
    >> 
    >>> $Day [1] 1 2 3 4 5 6
    >> 
    >> 
    >>> -pd
    >> 
    >>>> On 26 Jun 2017, at 04:40 , Hong Ooi via R-devel
    >>>> <r-devel at r-project.org> wrote:
    >>>> 
    >>>> The behaviour of within() with list input changes if
    >>>> you delete 2 or more variables, compared to deleting
    >>>> one:
    >>>> 
    >>>> l <- list(x=1, y=2, z=3)
    >>>> 
    >>>> within(l, { rm(z) }) #$x #[1] 1
    >>>> #
    >>>> #$y #[1] 2
    >>>> 
    >>>> 
    >>>> within(l, { rm(y) rm(z) }) #$x #[1] 1
    >>>> #
    >>>> #$y #NULL
    >>>> #
    >>>> #$z #NULL
    >>>> 
    >>>> 
    >>>> When 2 or more variables are deleted, the list entries
    >>>> are instead set to NULL. Is this intended?
    >>>> 
    >>>> ______________________________________________
    >>>> R-devel at r-project.org mailing list
    >>>> https://stat.ethz.ch/mailman/listinfo/r-devel
    >> 
    >>> -- 
    >>> Peter Dalgaard, Professor, Center for Statistics,
    >>> Copenhagen Business School Solbjerg Plads 3, 2000
    >>> Frederiksberg, Denmark Phone: (+45)38153501 Office: A
    >>> 4.23 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com
    >> 
    >> 
    >> 
    >> 
    >> 
    >> 
    >> 
    >> 

    PD> -- Peter Dalgaard, Professor, Center for Statistics,
    PD> Copenhagen Business School Solbjerg Plads 3, 2000
    PD> Frederiksberg, Denmark Phone: (+45)38153501 Office: A
    PD> 4.23 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com