[R] converting time format

[lily li]

Yes, it is a little different. Is there a way to get 'yyyy-mm' format?
Thanks.

On Wed, Feb 22, 2017 at 2:10 PM, Jim Lemon <drjimlemon at gmail.com> wrote:

> Hi Lily.
> Two problems. You have named the month field "mon" and then refer to
> it as "month". Second, as the resolution of as.Date is days, it can't
> produce a valid date without specifying the day. Thus:
>
> df.count.mon<-data.frame(count=sample(1:24,24),
>  year=rep(2014:2015,each=2),mon=rep(1:12,2))
> # make each day the first day of the month
> df.count.mon$time<-
>  as.Date(paste(df.count.mon$year, df.count.mon$mon,1),
>  '%Y %m %d')
> df.count.mon
>    count year mon       time
> 1     22 2014   1 2014-01-01
> 2     12 2014   2 2014-02-01
> ...
> You will get values, but I don't think they are the ones you want.
>
> Jim
>
> On Thu, Feb 23, 2017 at 6:33 AM, lily li <chocold12 at gmail.com> wrote:
> > Hi R users,
> >
> > I have a dataframe, with year, month, day, and other variables. I wanted
> to
> > calculated monthly values of the variables. For example, there is one
> > variable called 'count'. I use the code below to convert daily data to
> > monthly data.
> >
> > df.count.mon = aggregate(count ~ year+month, data= df, sum)
> >
> > The new dataframe has three columns: year, month, and count. Now I want
> to
> > add one more column as 'time', which has the format 'yyyy-mm'. I use the
> > code below but the new column has all NA values. What is the problem and
> > how to solve it?
> >
> > df.count.mon$time = as.Date(paste(df.count.mon$year,
> df.count.mon$month),
> > '%Y %m')
> >
> > I had experience to add one more column with the format 'yyyy-mm-dd',
> which
> > works, but not with monthly format. Thanks for your help.
> >
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> >
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