[R] write function to convert to date or delete

[William Dunlap]

> Error in as.POSIXlt.character(as.character(x), ...) :
>   character string is not in a standard unambiguous format.

That error occurs when as.POSIXlt is looking for a format
with which to parse the strings.  If you supply a format for the
date then as.POSIXlt will not give this error - it will just return
NA's for the entries that do not match the format.
   > as.POSIXlt(c("2013-02-28", "Feb 28, 2013"))
   Error in as.POSIXlt.character(c("2013-02-28", "Feb 28, 2013")) :
     character string is not in a standard unambiguous format
   > as.POSIXlt(c("2013-02-28", "Feb 28, 2013"), format="%Y-%m-%d")
   [1] "2013-02-28" NA
   > as.POSIXlt(c("2013-02-28", "Feb 28, 2013"), format="%B %d, %Y")
   [1] NA           "2013-02-28"

If the strings may be in one of several formats, loop through
the formats and decide which to accept. 

Bill Dunlap
TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Bill
> Sent: Wednesday, February 26, 2014 10:03 PM
> To: r-help at r-project.org
> Subject: [R] write function to convert to date or delete
> 
> I have a dataframe that looks like the below. I want to convert the
> Captured.Time  field to a date object. but some of the entries are not
> properly formated and I get a message saying
> Error in as.POSIXlt.character(as.character(x), ...) :
>   character string is not in a standard unambiguous format.
> 
> So I want to write a function that will convert or delete. I could not
> figure out how to do that and so I tried to write a function that would
> convert or replace with text like noDateHere but that did not work either.
> Can anyone tell me how to accomplish this?
> Here is what I tried:
> 
> convertOrOmit=function(dt){tryCatch(as.POSIXct(dt),error=print("noDateHere"))}
> 
>   X       Captured.Time Latitude Longitude Value Unit Location.Name
> 1 12696963 2012-08-07 11:00:51 39.16094  140.4883    45  cpm
> 2  2056198 2013-11-10 03:14:19 32.84428 -117.2240    47  cpm
> 3   727957 2014-01-28 04:47:54 35.80605  139.3789    28  cpm
> 4  2864220 2013-10-22 19:41:53 35.07816 -106.6123    50  cpm
> 5  5787688 2013-06-13 04:13:57 35.83174  136.2027    35  cpm
> 6  6191345 2013-05-28 06:48:34 34.78944  137.9496    32  cpm
>   Device.ID                           MD5Sum Height Surface Radiation
> 1        NA b0465019b46289b82450c39ce1397b98     NA                NA
> 2        NA 8fa14a1227d23e6cf286785e8843cc39     NA                NA
> 3        NA c72cd7f9cedd59cf6e6892049dfbf9a0     NA                NA
> 4        NA aca82e39ff9098e45eea04f661f68dc7     NA                NA
> 5        NA cc9394e6dceb91f0e0de97cc2db57e19     NA                NA
> 6        NA f18d194a41e1448c7776dbeba8b351af     NA                NA
>                Uploaded.Time Loader.ID
> 1  2012-08-13 19:16:10.18555     10832
> 2 2013-12-05 01:47:24.154971     13958
> 3 2014-01-29 22:55:39.138043     14451
> 4 2013-10-26 13:50:17.629869     13743
> 5 2013-06-16 16:17:21.148239     12930
> 6 2013-06-04 23:31:55.455323     12841
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> 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.