[R] Reading a datetime vector

[D Wolf]

Hello Jim,
I ran str() on the vector and it returned character:str("DF_exp.xlsx") chr "DF_exp.xlsx"
I tried df2_TZ$DateTimeStamp <- strptime(as.Date(as.character(df2_TZ$DateTimeStamp, format = "%m/%d/%Y %H:%M", tz = "GMT"))), which produced an error: Error in charToDate(x) :   character string is not in a standard unambiguous formatIn Excel, the column is formatted to m/d/yyyy h:mm
Removing %S from these linesdf2_TZ$DateTimeStamp = as.POSIXct(df2_TZ$DateTimeStamp, format="%m/%d/%Y %H:%M", tz="GMT") df2_TZ$DateTimeStamp = as.POSIXct(as.character(df2_TZ$DateTimeStamp), format = "%m/%d/%Y %H:%M")
made the column NA

Thank You,Doug Wolfinger


 

    On Friday, February 19, 2016 1:35 AM, Jim Lemon <drjimlemon at gmail.com> wrote:
 

 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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