[R] Reading a datetime vector

[Jeff Newmiller]

You are being rather scattershot in your explanation, so I suspect you are not being systematic in your troubleshooting. Use the str function to examine the data column after you pull it in from excel. It may be numeric, factor, or character, and the approach depends on which that function returns. 
-- 
Sent from my phone. Please excuse my brevity.

On February 18, 2016 1:12:40 PM PST, 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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