Dear Steve,
Multiplying the mean with the number of observations is essentially the same as
summing the numbers.
Have a look at the plyr packages.
library(plyr)
ddply(data, c("month", "year"), function(x){
c(MeanMultiplied = mean(x$ramm) * nrow(x), Sum = sum(x$ramm))
})
----------------------------------------------------------------------------
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek
team Biometrie & Kwaliteitszorg
Gaverstraat 4
9500 Geraardsbergen
Belgium
Research Institute for Nature and Forest
team Biometrics & Quality Assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
thierry.onkel...@inbo.be
www.inbo.be
To call in the statistician after the experiment is done may be no more than
asking him to perform a post-mortem examination: he may be able to say what the
experiment died of.
~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data.
~ Roger Brinner
The combination of some data and an aching desire for an answer does not ensure
that a reasonable answer can be extracted from a given body of data.
~ John Tukey
> -----Oorspronkelijk bericht-----
> Van: r-help-boun...@r-project.org
> [mailto:r-help-boun...@r-project.org] Namens Steve Murray
> Verzonden: vrijdag 2 april 2010 16:37
> Aan: stephan.kola...@gmx.de; gunter.ber...@gene.com
> CC: r-help@r-project.org
> Onderwerp: Re: [R] Summing data based on certain conditions
>
>
> Dear all,
>
> Thanks for the contributions so far. I've had a look at these
> and the closest I've come to solving it is the following:
>
> > data_ave <- ave(data$rammday, by=c(data$month, data$year))
> Warning messages:
> 1: In split.default(x, g) :
> data length is not a multiple of split variable
> 2: In split.default(seq_along(x), f, drop = drop, ...) :
> data length is not a multiple of split variable
>
>
> I'm slightly confused by the warning message, as the data
> lengths do appear the same:
>
> > dim(data)
> [1] 1073 6
> > length(data$year)
> [1] 1073
> > length(data$month)
> [1] 1073
>
>
> Maybe the approach I'm taking is wrong. Any suggestions would
> be gratefully received.
>
> Many thanks,
>
> Steve
>
>
> ----------------------------------------
> > Date: Wed, 31 Mar 2010 23:31:25 +0200
> > From: stephan.kola...@gmx.de
> > To: smurray...@hotmail.com
> > CC: r-help@r-project.org
> > Subject: Re: [R] Summing data based on certain conditions
> >
> > ?by may also be helpful.
> >
> > Stephan
> >
> >
> > Steve Murray schrieb:
> >> Dear all,
> >>
> >> I have a dataset of 1073 rows, the first 15 which look as follows:
> >>
> >>> data[1:15,]
> >> date year month day rammday thmmday
> >> 1 3/8/1988 1988 3 8 1.43 0.94
> >> 2 3/15/1988 1988 3 15 2.86 0.66
> >> 3 3/22/1988 1988 3 22 5.06 3.43
> >> 4 3/29/1988 1988 3 29 18.76 10.93
> >> 5 4/5/1988 1988 4 5 4.49 2.70
> >> 6 4/12/1988 1988 4 12 8.57 4.59
> >> 7 4/16/1988 1988 4 16 31.18 22.18
> >> 8 4/19/1988 1988 4 19 19.67 12.33
> >> 9 4/26/1988 1988 4 26 3.14 1.79
> >> 10 5/3/1988 1988 5 3 11.51 6.33
> >> 11 5/10/1988 1988 5 10 5.64 2.89
> >> 12 5/17/1988 1988 5 17 37.46 20.89
> >> 13 5/24/1988 1988 5 24 9.86 9.81
> >> 14 5/31/1988 1988 5 31 13.00 8.63
> >> 15 6/7/1988 1988 6 7 0.43 0.00
> >>
> >>
> >> I am looking for a way by which I can create monthly
> totals of rammday (rainfall in mm/day; column 5) by doing the
> following:
> >>
> >> For each case where the month value and the year are the
> same (e.g. 3 and 1988, in the first four rows), find the mean
> of the the corresponding rammday values and then times by the
> number of days in that month (i.e. 31 in this case).
> >>
> >> Note however that the number of month values in each case
> isn't always the same (e.g. in this subset of data, there are
> 4 values for month 3, 5 for month 4 and 5 for month 5). Also
> the months will of course recycle for the following years, so
> it's not simply a case of finding a monthly total for *all*
> the 3s in the whole dataset, just those associated with each
> year in turn.
> >>
> >> How would I go about doing this in R?
> >>
> >> Any help will be gratefully received.
> >>
> >> Many thanks,
> >>
> >> Steve
> >>
> >>
> >>
> >> _________________________________________________________________
> >> We want to hear all your funny, exciting and crazy Hotmail
> stories.
> >> Tell us now
> >>
> >> ______________________________________________
> >> R-help@r-project.org mailing list
> >> 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.
> >>
> >
>
> _________________________________________________________________
>
> Do you have a story that started on Hotmail? Tell us now
> ______________________________________________
> R-help@r-project.org mailing list
> 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.
>
Druk dit bericht a.u.b. niet onnodig af.
Please do not print this message unnecessarily.
Dit bericht en eventuele bijlagen geven enkel de visie van de schrijver weer
en binden het INBO onder geen enkel beding, zolang dit bericht niet bevestigd is
door een geldig ondertekend document. The views expressed in this message
and any annex are purely those of the writer and may not be regarded as stating
an official position of INBO, as long as the message is not confirmed by a duly
signed document.
______________________________________________
R-help@r-project.org mailing list
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.
