[R] roll weekly data to monthly level

[David Winsemius]

I had trouble getting my output to look like yours until I realized  
that you did not want "to sum up the weekly data to the monthly level"  
but rather to sum up to the monthly *and* ID level.

 > dftag<-aggregate(dft$y, list(ID=dft$ID, Month=as.yearmon(dft$time,  
"%m/%d/%Y")), FUN=sum)
# in Month order rather than ID, Month order
 > dftag[order(dftag$ID, dftag$Month), ]
   ID    Month  x
3  1 Feb 2008 16
7  1 Sep 2008  8
1  2 Jan 2008  3
5  2 Mar 2008 13
6  2 Jun 2008  4
2  3 Jan 2008 11
4  3 Feb 2008 10

-- 
David Winsemius

On Jan 12, 2009, at 4:57 PM, liujb wrote:

>
> Dear R users:
>
> I have a data set that looks something like this:
> ID    time           y
> 1    2/01/2008    4
> 1    2/09/2008    12
> 1    9/01/2008    8
> 2    1/06/2008    3
> 2    3/01/2008    4
> 2    3/09/2008    9
> 2    6/03/2008    4
> 3    1/02/2008    3
> 3    1/10/2008    8
> 3    2/02/2008    7
> 3    2/10/2008    3
>
> I'd like to sum up the weekly data to the monthly level, so that it  
> looks
> something like this:
>
> ID    time       y
> 1    2/2008    16
> 1    9/2008    8
> 2    1/2008    3
> 2    3/2008    13
> 2    6/2008    4
> 3    1/2008    11
> 3    2/2008    10
>
>
> What is the best way to do it?
>
> Time must be character. How do I truncate a character so that I can  
> remove
> the date and only keep the month and year?
>
> Thank you very much in advance.
> Julia
> -- 
> View this message in context: http://www.nabble.com/roll-weekly-data-to-monthly-level-tp21424700p21424700.html
> Sent from the R help mailing list archive at Nabble.com.
>
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