[R] Aggregating daily rainfall raster data to bimontly data

[Jim Lemon]

Hi John,
One way is to create an index variable that will divide your data into the
appropriate intervals. There are a number of ways to do this. Say you want
the "two month" version of bimonthly and you have a date variable
("raindate") for each observation like "1982-01-01".

date_order<-paste(rep(month.abb,30),rep(1982:2011,each=12),sep="")
month_index<-factor(format(as.Date(raindate,"%Y-%m-%d"),"%b%Y"),levels=date_order)

You can then subset the raster matrices by "month_index" and average them
for each group

Jim

On Mon, Apr 6, 2015 at 3:08 AM, Jeff Newmiller <jdnewmil at dcn.davis.ca.us>
wrote:

> Please stop posting using HTML (as the Posting Guide warns you), and
> follow John Kane's advice. Your reply below is not helping us understand as
> well as you seem to think it should.
> ---------------------------------------------------------------------------
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> Sent from my phone. Please excuse my brevity.
>
> On April 5, 2015 9:52:18 AM PDT, John Wasige <johnwasige at gmail.com> wrote:
> >Thanks Bert,
> >
> >The structure of the data is a raster stack with nraw=867, Ncol=995
> >
> >Rgds John
> >
> >
> >On Sun, Apr 5, 2015 at 6:39 PM, Bert Gunter <gunter.berton at gene.com>
> >wrote:
> >
> >> See ?tapply
> >>
> >> However, as John said, without knowing the structure of your data, it
> >> is impossible to provide a guaranteed recipe. For example, does the
> >> data structure contain date information? -- it would be difficult
> >(but
> >> not impossible depending on data structure) to aggregate by calendar
> >> (bi-monthly, depending on your meaning of "bi") without knowing the
> >> months. Aggregating by every n days would be easy, but that's
> >probably
> >> not what you want.
> >>
> >> Cheers,
> >> Bert
> >>
> >> Bert Gunter
> >> Genentech Nonclinical Biostatistics
> >> (650) 467-7374
> >>
> >> "Data is not information. Information is not knowledge. And knowledge
> >> is certainly not wisdom."
> >> Clifford Stoll
> >>
> >>
> >>
> >>
> >> On Sun, Apr 5, 2015 at 9:13 AM, John Kane <jrkrideau at inbox.com>
> >wrote:
> >> > Someone might if they had any idea of what the data actually looked
> >like
> >> and what you are trying to do. The 'bimonthly' for example, is
> >ambiguous in
> >> English; do you mean every two months or twice a month?
> >> >
> >> > Have a look at
> >https://github.com/hadley/devtools/wiki/Reproducibility
> >> and
> >>
> >
> http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example
> >> with special attention to dput() as a method of supplying sample data
> >to
> >> the help list.
> >> >
> >> > John Kane
> >> > Kingston ON Canada
> >> >
> >> >
> >> >> -----Original Message-----
> >> >> From: johnwasige at gmail.com
> >> >> Sent: Sun, 5 Apr 2015 11:34:30 +0200
> >> >> To: r-help at r-project.org
> >> >> Subject: [R] Aggregating daily rainfall raster data to bimontly
> >data
> >> >>
> >> >> Dear community,
> >> >>
> >> >> I have daily rainfall raster data for 30 years (1982_2011). I
> >would like
> >> >> to
> >> >> aggregate daily to bimonthly raster data. Could somebody kindly
> >help on
> >> >> how
> >> >> to go about it!
> >> >>
> >> >> Thanks for your help
> >> >>
> >> >> --
> >> >> John
> >> >>
> >> >>       [[alternative HTML version deleted]]
> >> >>
> >> >> ______________________________________________
> >> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> >> PLEASE do read the posting guide
> >> >> http://www.R-project.org/posting-guide.html
> >> >> and provide commented, minimal, self-contained, reproducible code.
> >> >
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> >> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> >> > PLEASE do read the posting guide
> >> http://www.R-project.org/posting-guide.html
> >> > and provide commented, minimal, self-contained, reproducible code.
> >>
> >
> >       [[alternative HTML version deleted]]
> >
> >______________________________________________
> >R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >https://stat.ethz.ch/mailman/listinfo/r-help
> >PLEASE do read the posting guide
> >http://www.R-project.org/posting-guide.html
> >and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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