POSIXlt class and lapply

4 messages · William Dunlap, Newell, Paul, Ista Zahn

Original

1

4

Newell, Paul

Thu, Feb 14, 2019 7:28 AM #

Dear R-helpers,

We have recently upgraded from R-3.3.1 to R-3.5.2.

It seems there has been a change in behaviour of `lapply` and the `POSIXlt` class that I cannot find explicitly documented.


In R-3.3.1:

$sec
[1] 1
$min
[1] 1
$hour
[1] 1
$mday
[1] 1
$mon
[1] 1
$year
[1] 1
$wday
[1] 1
$yday
[1] 1
$isdst
[1] 1


whereas, in R-3.5.2:

[[1]]
[1] 1


Is this change in behaviour intentional?

Realistically, I cannot see anything documented to say that `lapply` should behave as per R-3.3.1 on a `POSIXlt` object, so it is/was perhaps unwise to rely on it.


Best wishes,
Paul Newell

Thu, Feb 14, 2019 12:03 PM #

Somewhere between R-3.3.3 and R-3.5.2 a POSIXlt method for as.list() was
added, and lapply probably calls as.list().

R version 3.3.3 (2017-03-06)                        | R version 3.5.1
(2018-07-02)
[1] as.list.data.frame      as.list.Date            | [1]
as.list.data.frame      as.list.Date
[3] as.list.default         as.list.environment     | [3] as.list.default
       as.list.environment
[5] as.list.factor          as.list.function        | [5] as.list.factor
      as.list.function
[7] as.list.numeric_version as.list.POSIXct         | [7]
as.list.numeric_version as.list.POSIXct
see '?methods' for accessing help and source code   | [9] as.list.POSIXlt
                                                    | see '?methods' for
accessing help and source code


Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Thu, Feb 14, 2019 at 9:45 AM Newell, Paul <paul.newell at metoffice.gov.uk>
wrote:

______________________________________________
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http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Newell, Paul

Fri, Feb 15, 2019 4:15 AM #

Many thanks Bill Dunlap.

You are correct that `lapply` calls `as.list`, which I should have seen if I had looked a little harder.

Whether that would have led me to locate `as.list.POSIXlt` is another matter.

Best wishes.



From: William Dunlap <wdunlap at tibco.com>
Sent: 14 February 2019 20:03
To: Newell, Paul
Cc: r-help at r-project.org
Subject: Re: [R] POSIXlt class and lapply
?
Somewhere between R-3.3.3 and R-3.5.2 a POSIXlt method for as.list() was added, and lapply probably calls as.list().

R version 3.3.3 (2017-03-06)? ? ? ? ? ? ? ? ? ? ? ? | R version 3.5.1 (2018-07-02)
[1] as.list.data.frame? ? ? as.list.Date? ? ? ? ? ? | [1] as.list.data.frame? ? ? as.list.Date
[3] as.list.default? ? ? ? ?as.list.environment? ? ?| [3] as.list.default? ? ? ? ?as.list.environment
[5] as.list.factor? ? ? ? ? as.list.function? ? ? ? | [5] as.list.factor? ? ? ? ? as.list.function
[7] as.list.numeric_version as.list.POSIXct? ? ? ? ?| [7] as.list.numeric_version as.list.POSIXct
see '?methods' for accessing help and source code? ?| [9] as.list.POSIXlt
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? | see '?methods' for accessing help and source code




Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Thu, Feb 14, 2019 at 9:45 AM Newell, Paul <paul.newell at metoffice.gov.uk> wrote:

Dear R-helpers,

We have recently upgraded from R-3.3.1 to R-3.5.2.

It seems there has been a change in behaviour of `lapply` and the `POSIXlt` class that I cannot find explicitly documented.


In R-3.3.1:

$sec
[1] 1
$min
[1] 1
$hour
[1] 1
$mday
[1] 1
$mon
[1] 1
$year
[1] 1
$wday
[1] 1
$yday
[1] 1
$isdst
[1] 1


whereas, in R-3.5.2:

[[1]]
[1] 1


Is this change in behaviour intentional?

Realistically, I cannot see anything documented to say that `lapply` should behave as per R-3.3.1 on a `POSIXlt` object, so it is/was perhaps unwise to rely on it.


Best wishes,
Paul Newell
______________________________________________
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.

Ista Zahn

Fri, Feb 15, 2019 5:55 AM #

As a practical matter, you can't treat POSIXlt as a list. The
documentation could be clearer about this.  ?DateTimeClasses says

"Class ?"POSIXlt"? is a named list of vectors", and then later, "Note
that the internal list structure is somewhat hidden, as many methods
(including ?length(x)?, ?print()? and ?str?) apply to the abstract
date-time vector, as for ?"POSIXct"?."

In other words, "POSIXct" is internally a list, but you can't really
treat it as one. If you want to access the internal list structure
directly, unclass it for first. For example:

[1] 20

[1] 11

POSIXlt[1:20], format: "2019-02-15 08:53:16" "2019-02-15 08:53:15"
"2019-02-15 08:53:14" ...

List of 11
 $ sec   : num [1:20] 16.9 15.9 14.9 13.9 12.9 ...
 $ min   : int [1:20] 53 53 53 53 53 53 53 53 53 53 ...
 $ hour  : int [1:20] 8 8 8 8 8 8 8 8 8 8 ...
 $ mday  : int [1:20] 15 15 15 15 15 15 15 15 15 15 ...
 $ mon   : int [1:20] 1 1 1 1 1 1 1 1 1 1 ...
 $ year  : int [1:20] 119 119 119 119 119 119 119 119 119 119 ...
 $ wday  : int [1:20] 5 5 5 5 5 5 5 5 5 5 ...
 $ yday  : int [1:20] 45 45 45 45 45 45 45 45 45 45 ...
 $ isdst : int [1:20] 0 0 0 0 0 0 0 0 0 0 ...
 $ zone  : chr [1:20] "EST" "EST" "EST" "EST" ...
 $ gmtoff: int [1:20] -18000 -18000 -18000 -18000 -18000 -18000 -18000
-18000 -18000 -18000 ...
 - attr(*, "tzone")= chr [1:3] "" "EST" "EDT"

[1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

sec    min   hour   mday    mon   year   wday   yday  isdst   zone gmtoff
    20     20     20     20     20     20     20     20     20     20     20

Best,
Ista

On Fri, Feb 15, 2019 at 7:15 AM Newell, Paul

<paul.newell at metoffice.gov.uk> wrote:

Many thanks Bill Dunlap.

You are correct that `lapply` calls `as.list`, which I should have seen if I had looked a little harder.

Whether that would have led me to locate `as.list.POSIXlt` is another matter.

Best wishes.



From: William Dunlap <wdunlap at tibco.com>
Sent: 14 February 2019 20:03
To: Newell, Paul
Cc: r-help at r-project.org
Subject: Re: [R] POSIXlt class and lapply

Somewhere between R-3.3.3 and R-3.5.2 a POSIXlt method for as.list() was added, and lapply probably calls as.list().

RCompare(methods("as.list"))

R version 3.3.3 (2017-03-06)                        | R version 3.5.1 (2018-07-02)
[1] as.list.data.frame      as.list.Date            | [1] as.list.data.frame      as.list.Date
[3] as.list.default         as.list.environment     | [3] as.list.default         as.list.environment
[5] as.list.factor          as.list.function        | [5] as.list.factor          as.list.function
[7] as.list.numeric_version as.list.POSIXct         | [7] as.list.numeric_version as.list.POSIXct
see '?methods' for accessing help and source code   | [9] as.list.POSIXlt
                                                    | see '?methods' for accessing help and source code




Bill Dunlap
TIBCO Software
wdunlap tibco.com




On Thu, Feb 14, 2019 at 9:45 AM Newell, Paul <paul.newell at metoffice.gov.uk> wrote:

Dear R-helpers,

We have recently upgraded from R-3.3.1 to R-3.5.2.

It seems there has been a change in behaviour of `lapply` and the `POSIXlt` class that I cannot find explicitly documented.


In R-3.3.1:

lapply(as.POSIXlt(Sys.Date()), length)

$sec
[1] 1
$min
[1] 1
$hour
[1] 1
$mday
[1] 1
$mon
[1] 1
$year
[1] 1
$wday
[1] 1
$yday
[1] 1
$isdst
[1] 1


whereas, in R-3.5.2:

lapply(as.POSIXlt(Sys.Date()), length)

[[1]]
[1] 1


Is this change in behaviour intentional?

Realistically, I cannot see anything documented to say that `lapply` should behave as per R-3.3.1 on a `POSIXlt` object, so it is/was perhaps unwise to rely on it.


Best wishes,
Paul Newell

______________________________________________
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.

______________________________________________
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.