[R] extract certain months toyears (zoo)

[Gabor Grothendieck]

Please read the last line to every post on r-help particularly
noting the reproducible part.

Assuming you have a series such as z below and want
June, July and August of each year:

> library(zoo)
> set.seed(1)
> z <- zoo(rnorm(25), as.yearmon("2000-01") + 0:24/12)
> z[format(time(z), "%m") %in% c("06", "07", "08")]
  Jun 2000   Jul 2000   Aug 2000   Jun 2001   Jul 2001   Aug 2001
-0.8204684  0.4874291  0.7383247  0.9438362  0.8212212  0.5939013

On Fri, Jan 23, 2009 at 6:52 AM, Bastian Pöschl <rotate at gmx.li> wrote:
> Dear useRs and developeRs,
> In my diploma thesis I work with a daily time series of glacier runoff
> data.
> I did already aggregate them to monthly means etc.
> Now i want to use just the summer values (I am  indecisive  by now what
> that means, but let's make it easy and use months like June).
> Is there a way to extract the data off this zoo into another zoo with
> frequency=1 ?
>
> Do you have alternative suggestions how to get to such data??
>
>
> what i did...
>
> #########################################################
> ## want to create monthly aggr. and extract the summer data
> #########################################################
> library(zoo)
> a.z<- read.zoo("glacierdischarge.txt", header=TRUE, sep=",", dec = ".",
> na.string="NA", format = "%d.%m.%Y")
> a.z.mean <- aggregate(a.z, as.yearmon, mean)
> a.z.median <- aggregate(a.z, as.yearmon, median)
> a.z.sd <- aggregate(a.z, as.yearmon, sd)
> a.z.min <- aggregate(a.z, as.yearmon, min)
> a.z.max <- aggregate(a.z, as.yearmon, max)
> a.z.sum <- aggregate(a.z, as yearmon, sum)
> a.zoo<-cbind(mean = a.z.mean, median= a.z.median, sd = a.z.sd, min=
> a.z.min, max= a.z.max)
> head(a.zoo)
>
>
> I tried it with merge and...
>
> ##vector including all junes
> l<-length(a.zoo$mean)
> Junes<-seq(6, l, by = 12)
>
> but stuck.
>
> Hopefully
>
> Bastian
>
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