[R] converting time format

[Jim Lemon]

Sure:

df.count.mon$time<-format(as.Date(paste(df.count.mon$year,  df.count.mon$mon,1),
 '%Y %m %d'),"%Y %m")
> df.count.mon
   count year mon    time
1     22 2014   1 2014 01
2     12 2014   2 2014 02
...

Jim

On Thu, Feb 23, 2017 at 8:18 AM, lily li <chocold12 at gmail.com> wrote:
> 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.
>> >
>> >         [[alternative HTML version deleted]]
>> >
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>