[R] Why is there error in as.POSIXlt.character when using strftime()?

[William Dunlap]

Note that the first unparsable element is the first with a 13 in the second
field, which is out of range for the month entry.  If you look at the the
whole date/time output by the first 19 elements you will see that you need
to tell it the order of the year, month, and day

> as.POSIXlt(dat[1:19])
 [1] "0007-12-15 11:32:00 LMT" "0007-12-15 11:42:00 LMT"
 [3] "0007-12-15 12:17:00 LMT" "0007-12-15 12:31:00 LMT"
 [5] "0007-12-15 12:50:00 LMT" "0007-12-15 14:10:00 LMT"
 [7] "0007-12-15 14:19:00 LMT" "0007-12-15 14:59:00 LMT"
 [9] "0007-12-15 15:57:00 LMT" "0007-12-15 16:00:00 LMT"
[11] "0007-12-15 16:46:00 LMT" "0007-12-15 16:51:00 LMT"
[13] "0007-12-15 17:35:00 LMT" "0007-12-15 17:59:00 LMT"
[15] "0007-12-15 18:17:00 LMT" "0007-12-15 19:07:00 LMT"
[17] "0007-12-15 19:08:00 LMT" "0007-12-15 19:31:00 LMT"
[19] "0007-12-15 21:21:00 LMT"
> as.POSIXlt(dat, format="%m/%d/%y %H:%M")
 [1] "2015-07-12 11:32:00 PDT" "2015-07-12 11:42:00 PDT"
 [3] "2015-07-12 12:17:00 PDT" "2015-07-12 12:31:00 PDT"
 [5] "2015-07-12 12:50:00 PDT" "2015-07-12 14:10:00 PDT"
 [7] "2015-07-12 14:19:00 PDT" "2015-07-12 14:59:00 PDT"
 [9] "2015-07-12 15:57:00 PDT" "2015-07-12 16:00:00 PDT"
[11] "2015-07-12 16:46:00 PDT" "2015-07-12 16:51:00 PDT"
[13] "2015-07-12 17:35:00 PDT" "2015-07-12 17:59:00 PDT"
[15] "2015-07-12 18:17:00 PDT" "2015-07-12 19:07:00 PDT"
[17] "2015-07-12 19:08:00 PDT" "2015-07-12 19:31:00 PDT"
[19] "2015-07-12 21:21:00 PDT" "2015-07-13 06:00:00 PDT"
[21] "2015-07-13 06:20:00 PDT" "2015-07-13 06:37:00 PDT"
[23] "2015-07-13 06:40:00 PDT" "2015-07-13 06:46:00 PDT"
[25] "2015-07-13 07:20:00 PDT" "2015-07-13 07:47:00 PDT"
[27] "2015-07-13 07:50:00 PDT" "2015-07-13 07:54:00 PDT"
[29] "2015-07-13 08:11:00 PDT" "2015-07-13 08:23:00 PDT"
[31] "2015-07-13 08:31:00 PDT" "2015-07-13 08:33:00 PDT"
[33] "2015-07-13 08:43:00 PDT" "2015-07-13 09:04:00 PDT"
[35] "2015-07-13 09:09:00 PDT" "2015-07-13 09:30:00 PDT"
[37] "2015-07-13 09:59:00 PDT" "2015-07-13 10:01:00 PDT"
[39] "2015-07-13 10:03:00 PDT" "2015-07-13 10:05:00 PDT"

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Sat, Feb 2, 2019 at 6:46 AM C W <tmrsg11 using gmail.com> wrote:

> Dear R community,
>
> I am working with dates. And I get the following error:
> > strftime(dat[20], format="%H:%M")
> Error in as.POSIXlt.character(as.character(x), ...) :
>   character string is not in a standard unambiguous format
>
> Here's the original data:
> dat <- structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L,
> 13L, 14L, 15L, 16L, 17L, 18L, 19L, 23L, 24L, 25L, 26L, 27L, 28L,
> 29L, 30L, 31L, 32L, 33L, 34L, 35L, 36L, 37L, 38L, 39L, 40L, 20L,
> 21L, 22L), .Label = c("7/12/15 11:32", "7/12/15 11:42", "7/12/15 12:17",
> "7/12/15 12:31", "7/12/15 12:50", "7/12/15 14:10", "7/12/15 14:19",
> "7/12/15 14:59", "7/12/15 15:57", "7/12/15 16:00", "7/12/15 16:46",
> "7/12/15 16:51", "7/12/15 17:35", "7/12/15 17:59", "7/12/15 18:17",
> "7/12/15 19:07", "7/12/15 19:08", "7/12/15 19:31", "7/12/15 21:21",
> "7/13/15 10:01", "7/13/15 10:03", "7/13/15 10:05", "7/13/15 6:00",
> "7/13/15 6:20", "7/13/15 6:37", "7/13/15 6:40", "7/13/15 6:46",
> "7/13/15 7:20", "7/13/15 7:47", "7/13/15 7:50", "7/13/15 7:54",
> "7/13/15 8:11", "7/13/15 8:23", "7/13/15 8:31", "7/13/15 8:33",
> "7/13/15 8:43", "7/13/15 9:04", "7/13/15 9:09", "7/13/15 9:30",
> "7/13/15 9:59"), class = "factor")
>
> It seems like things work fine for the first 19 elements,
> > strftime(dat[1:19], format="%H:%M")
>  [1] "11:32" "11:42" "12:17" "12:31" "12:50" "14:10" "14:19" "14:59"
>  [9] "15:57" "16:00" "16:46" "16:51" "17:35" "17:59" "18:17" "19:07"
> [17] "19:08" "19:31" "21:21"
>
> But why not element 20 and on? They *look* the same to me.
>
> What is going on?
>
> Thanks very much!
>
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>
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