[R] Reading a datetime vector

[Jim Lemon]

Hi Doug,
For one thing, you may be using the wrong format. Your example format has
no seconds field. The other thing to watch is whether the data are in
%m/%d/%Y or %d/%m/%Y date format. If the latter, you would probably get
that error on dates like 19/02/2016.

Jim


On Fri, Feb 19, 2016 at 8:12 AM, D Wolf via R-help <r-help at r-project.org>
wrote:

> Hello,I am trying to read a data frame column named DateTimeStamp. The
> time is in GMT in this format: 1/4/2013 23:30
> require(xlsx)
> df2_TZ = read.xlsx2("DF_exp.xlsx", sheetName = "Sheet1")
>
> It's good to that line. But these three lines, which makes the dataframe,
> converts the column's values to NA:df2_TZ$DateTimeStamp =
> as.POSIXct(df2_TZ$DateTimeStamp, format="%m/%d/%Y %H:%M:%S", tz="GMT")
>
> and... df2_TZ$DateTimeStamp =
> as.POSIXct(as.character(df2_TZ$DateTimeStamp), format = "%m/%d/%Y %H:%M:%S")
>
> and...df2_TZ$DateTimeStamp = as.Date(df2_TZ$DateTimeStamp, format =
> "%m/%d/%Y %H:%M:%S")
>
> This line returns and error...df2_TZ$DateTimeStamp =
> as.POSIXct(as.Date(df2_TZ$DateTimeStamp), format = "%m/%d/%Y %H:%M:%S")
> "Error in charToDate(x) :   character string is not in a standard
> unambiguous format"
> Additionally, I need to convert from GMT to North American time zones, and
> I think the advice on this page would be good for that:
> http://blog.revolutionanalytics.com/2009/06/converting-time-zones.html
> My ultimate goal is to write an R program that finds data in another
> variable in df2_TZ that corresponds to a date and time that match up with
> the date and time in another data frame. For now, any help reading the
> column would be much appreciated.
> Thank You,Doug
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>
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