[R] Date Time in R

[Shivi Bhatia]

Thanks Marc for the help. this really helps.
I think there is some issue with the data saved in csv format for this
variable as when i checked:
str(eir$date)- this results in :-
Date[1:5327], format: NA NA NA NA NA.

Thanks again.

On Tue, Jul 26, 2016 at 5:58 PM, Marc Schwartz <marc_schwartz at me.com> wrote:

> Hi,
>
> That eir$date might be a factor is irrelevant. There is an as.Date()
> method for factors, which does the factor to character coercion internally
> and then calls as.Date.character() on the result.
>
> Using the example data below:
>
> eir <- data.frame(date = c("05-30-16", "05-30-16", "05-30-16",
>                            "05-30-16", "05-30-16", "05-30-16"))
>
> > str(eir)
> 'data.frame':   6 obs. of  1 variable:
>  $ date: Factor w/ 1 level "05-30-16": 1 1 1 1 1 1
>
> > eir
>       date
> 1 05-30-16
> 2 05-30-16
> 3 05-30-16
> 4 05-30-16
> 5 05-30-16
> 6 05-30-16
>
> eir$date <- as.Date(eir$date, format = "%m-%d-%y")
>
> > str(eir)
> 'data.frame':   6 obs. of  1 variable:
>  $ date: Date, format: "2016-05-30" ...
>
> > eir
>         date
> 1 2016-05-30
> 2 2016-05-30
> 3 2016-05-30
> 4 2016-05-30
> 5 2016-05-30
> 6 2016-05-30
>
> eir$days <- weekdays(eir$date)
>
> > str(eir)
> 'data.frame':   6 obs. of  2 variables:
>  $ date: Date, format: "2016-05-30" ...
>  $ days: chr  "Monday" "Monday" "Monday" "Monday" ...
>
> > eir
>         date   days
> 1 2016-05-30 Monday
> 2 2016-05-30 Monday
> 3 2016-05-30 Monday
> 4 2016-05-30 Monday
> 5 2016-05-30 Monday
> 6 2016-05-30 Monday
>
>
> I would check to be sure that you do not have any typos in your code.
>
> Regards,
>
> Marc Schwartz
>
>
> > On Jul 26, 2016, at 6:58 AM, Shivi Bhatia <shivipmp82 at gmail.com> wrote:
> >
> > Hello Again,
> >
> > While i tried your solution as you suggested above it seems to be
> working.
> > Here is the output
> > temp<- dput(head(eir$date))
> > c("05-30-16", "05-30-16", "05-30-16", "05-30-16", "05-30-16", "05-30-16")
> > however it still shows class(eir$date) as character and hence i cannot
> find
> > weekdays from this variable.
> >
> > Sorry but i still dont understand in totality how R reads dates even
> though
> > have tried enough.
> >
> > Regards, Shivi
> >
> >
> > On Tue, Jul 26, 2016 at 5:12 PM, Shivi Bhatia <shivipmp82 at gmail.com>
> wrote:
> >
> >> Thanks Duncan for the quick response. I will check again as you
> suggested.
> >> If that doesn't work i will share a reproducible example.
> >>
> >> Thanks again!!!!
> >>
> >> On Tue, Jul 26, 2016 at 4:43 PM, Duncan Murdoch <
> murdoch.duncan at gmail.com>
> >> wrote:
> >>
> >>> On 26/07/2016 7:05 AM, Shivi Bhatia wrote:
> >>>
> >>>> Hi Team,
> >>>>
> >>>> This scenario may have come across a number of times however i checked
> >>>> nabble & SO and couldn't find a solution hence request assistance.
> >>>>
> >>>> I have a date variable in my data-set eir. The class of this var was
> >>>> character while i had read the file in r studio. Example of date -
> >>>> 05-30-16
> >>>>
> >>>> To change this i have used eir$date<- as.Date(eir$date, "%m-%d-%y").
> This
> >>>> converts it to a date variable. However when i check few obs
> >>>> with head(eir$date) all the results are <NA>.
> >>>>
> >>>
> >>> I think you don't have character data like that, because I see
> >>>
> >>>> as.Date("05-30-16", "%m-%d-%y")
> >>> [1] "2016-05-30"
> >>>
> >>> I'd guess eir$date is really a factor, because character data is
> >>> frequently changed to factor automatically.  If that's the case, this
> >>> should work for the conversion:
> >>>
> >>> as.Date(as.character(eir$date), "%m-%d-%y")
> >>>
> >>> If that doesn't work, you'll need to post something reproducible.
> >>>
> >>> Duncan Murdoch
> >>>
> >>> I also need to create weekdays from this date variable but until i get
> >>>> this
> >>>> resolved i cant find a weekday. For weekday i have used:
> >>>> eir$week<- (eir$date)
> >>>> eir$week<- weekdays(as.Date(eir$week))
> >>>> class(eir$week)
> >>>> eir$week<- as.factor(eir$week)
> >>>> head(eir$week)
> >>>>
> >>>> Head of this eir$week results again as expected in <NA> but shows
> Levels:
> >>>> Friday Monday Saturday Sunday Thursday Tuesday Wednesday
> >>>>
> >>>> Not sure what i should do here. Kindly suggest.
>
>

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