[R] Date/Time to date & time

[Mark Knecht]

Thanks Gabor,
   I did try to use dput but it wasn't cooperating and wanted to send
FAR too much data.

   Your method works well for me but as I look at it I don't
understand the use of double brackets - DF[[1]] - why do you do that?

   Anyway, thanks for the fast reponses from you and Jim. Both will
allow me to make some headway today.

Cheers,
Mark

On Sun, Sep 20, 2009 at 1:27 PM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> Note that your explanation refers to strptime but the code uses
> strftime which accounts for the error.
>
> Try this:
>
>> Lines <- "ENTRY DATE
> + 3/23/2009 6:30:00 AM
> + 3/23/2009 6:30:00 AM
> + 3/23/2009 6:39:00 AM
> + 3/23/2009 6:39:00 AM
> + 3/23/2009 6:48:00 AM
> + 3/23/2009 6:48:00 AM
> + 3/23/2009 7:00:00 AM"
>>
>> DF <- read.csv(textConnection(Lines))
>> library(chron)
>> ch <- as.chron(as.character(DF[[1]]), "%m/%d/%Y %I:%M:%S %p")
>> dd <- dates(ch)
>> data.frame(Date = dd, Time = times(ch - dd))
>      Date     Time
> 1 03/23/09 06:30:00
> 2 03/23/09 06:30:00
> 3 03/23/09 06:39:00
> 4 03/23/09 06:39:00
> 5 03/23/09 06:48:00
> 6 03/23/09 06:48:00
> 7 03/23/09 07:00:00
>
> Try using dput next time to facilitate copying of your data into
> readers' sessions.
>
>> dput(DF)
> structure(list(ENTRY.DATE = structure(c(1L, 1L, 2L, 2L, 3L, 3L,
> 4L), .Label = c("3/23/2009 6:30:00 AM", "3/23/2009 6:39:00 AM",
> "3/23/2009 6:48:00 AM", "3/23/2009 7:00:00 AM"), class = "factor")),
> .Names = "ENTRY.DATE", class = "data.frame", row.names = c(NA,
> -7L))
>
> In the above we used dates and times classes from chron.  as.Date(x) will
> convert an object to Date class if you want that instead.
>
> See R News 4/1 for more on dates and times.
>
> On Sun, Sep 20, 2009 at 4:11 PM, Mark Knecht <markknecht at gmail.com> wrote:
>> Hi,
>>    Can strptime (or some other function) help me turn the following
>> column of a data.frame into two new columns, one as date and the other
>> as time, preserving the AM/PM value?
>>
>> Thanks,
>> Mark
>>
>>> B
>>              ENTRY DATE
>> 1  3/23/2009 6:30:00 AM
>> 2  3/23/2009 6:30:00 AM
>> 3  3/23/2009 6:39:00 AM
>> 4  3/23/2009 6:39:00 AM
>> 5  3/23/2009 6:48:00 AM
>> 6  3/23/2009 6:48:00 AM
>> 7  3/23/2009 7:00:00 AM
>>
>>> strftime(B, tz="", format="%m/%d/%Y %I:%M:%s %p")
>> Error in as.POSIXlt.default(x, tz = tz) :
>>  do not know how to convert 'x' to class "POSIXlt"
>>>
>>
>>> strptime(B, format="%m/%d/%Y %I:%M:%s %p")
>> [1] NA
>>>
>>
>>> mode(B)
>> [1] "list"
>>> class(B)
>> [1] "data.frame"
>>>
>>
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>>
>