R help - Jul 2018 - Locating data source error in large file

The structure of the dataframe is

str(wy2016)
'data.frame':	8784 obs. of  4 variables:
  $ date  : chr  "2015-10-01" "2015-10-01"
"2015-10-01" "2015-10-01" ...
  $ time  : chr  "00:00" "01:00" "02:00"
"03:00" ...
  $ elev  : num  90.7 90.7 90.7 90.7 90.7 ...
  $ myDate: Date, format: "2015-10-01" "2015-10-01" ...

   The command and results on this dataframe is:
wy2016$myTime <- as.POSIXct(paste(wy2016$date, wy2016$time))
Error in as.POSIXlt.character(x, tz, ...) :
   character string is not in a standard unambiguous format

   Data for other water years do not throw this error. How can I identify
which row(s) among the 8784 have a date or time formatting error?

Rich

The problem occurs because no commonly used format works on
all your date strings.  If you give as.POSIXlt the format you want to
use then items that don't match the format will be treated as NA's.
Use is.na() to find them.
> d <- c("2017-12-25", "2018-01-01",
"10/31/2018")
> as.POSIXlt(d)
Error in as.POSIXlt.character(d) :
  character string is not in a standard unambiguous
format
> as.POSIXlt(d, format="%Y-%m-%d")
[1] "2017-12-25 PST" "2018-01-01 PST"
NA
> as.POSIXlt(d, format="%m/%d/%Y")
[1] NA               NA               "2018-10-31 PDT"



Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Fri, Jul 20, 2018 at 10:43 AM, Rich Shepard <rshepard at
appl-ecosys.com>
wrote:
>   The structure of the dataframe is
>
> str(wy2016)
> 'data.frame':   8784 obs. of  4 variables:
>  $ date  : chr  "2015-10-01" "2015-10-01"
"2015-10-01" "2015-10-01" ...
>  $ time  : chr  "00:00" "01:00" "02:00"
"03:00" ...
>  $ elev  : num  90.7 90.7 90.7 90.7 90.7 ...
>  $ myDate: Date, format: "2015-10-01" "2015-10-01" ...
>
>   The command and results on this dataframe is:
> wy2016$myTime <- as.POSIXct(paste(wy2016$date, wy2016$time))
> Error in as.POSIXlt.character(x, tz, ...) :
>   character string is not in a standard unambiguous format
>
>   Data for other water years do not throw this error. How can I identify
> which row(s) among the 8784 have a date or time formatting error?
>
> Rich
>
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> and provide commented, minimal, self-contained, reproducible code.
>
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On Fri, 20 Jul 2018, William Dunlap wrote:
> The problem occurs because no commonly used format works on all your date
> strings. If you give as.POSIXlt the format you want to use then items that
> don't match the format will be treated as NA's. Use is.na() to find
them.
Bill,

   No NAs found using both is.na() and scrolling through the source file.
That's why I asked for help: I saw nothing different in the dates or times.

Regards,

Rich