Try this:
library(zoo)
z <- as.zoo(AirPassengers)
time(z) <- as.yearmon(time(z))
ix <- cycle(as.ts(z)) %in% c(3:5, 10:11)
aggregate(z[ix], floor, sum)
or this:
ix <- format(time(z), "%m") %in% c("03", "04", "05", "10", "11")
aggregate(z[ix], floor, sum)
It would be best if next time you posted some sample data.
On Tue, May 11, 2010 at 11:10 PM, Zablone Owiti <zow...@ncst.go.ke> wrote:
> Dear Users,
>
> I have a monthly data for a number of years(1960-2007) for a number of
> stations and i wish to extract sesonal time-series for the months of
> March-May and October-November for very station. I have read this data with
> read.table in R with stations as columns and time (months) as rows. My
> attempt to aggregate with the zoo package using the function as.yearqtr
> failed since this sums evey three months of the year from January. Is there
> away it can be coersed to aggregate particular months as in my case?
>
> Thanks
>
> ----------------------------
> ZABLONE OWITI
> GRADUATE STUDENT
> College of Atmospheric Science
> Nanjing University of Information, Science and Technology
> Add: 219 Ning Liu Rd, Nanjing, Jiangsu, 21004, P.R. China
> Tel: +86-25-58731402
> Fax: +86-25-58731456
> Mob. 15077895632
> Website: www.nuist.edu.cn
> ====================================================
>
>
> [[alternative HTML version deleted]]
>
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>
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