?cumsum can help you
m1 <- cbind(1:5,1:5,1:5)
m2 <- m1
for(i in 2:ncol(m1)){
m2[,i]=apply(m1[,1:i],1,sum)
}
m3 <- t(apply(m1, 1, cumsum))
all.equal(m2, m3)
HTH,
Thierry
----------------------------------------------------------------------------
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 Eleni Rapsomaniki
> Verzonden: woensdag 14 april 2010 14:18
> Aan: r-help@r-project.org
> Onderwerp: [R] Running cumulative sums in matrices
>
>
> Dear R-helpers,
>
> I have a huge data-set so need to avoid for loops as much as
> possible. Can someone think how I can compute the result in
> the following example (that uses a for-loop) using some
> version of apply instead (or any other similarly
> super-efficient function)?
>
> example:
> #Suppose a matrix:
> m1=cbind(1:5,1:5,1:5)
>
> #The aim is to create a new matrix with every column
> containing the cumulative sum of all previous columns.
> m2=m1
> for(i in 2:ncol(m1)){
> m2[,i]=apply(m1[,1:i],1,sum)
> }
> m2
>
> Many thanks in advance
>
> Eleni Rapsomaniki
>
> Research Associate
> Strangeways Research Laboratory
> Department of Public Health and Primary Care University of Cambridge
>
>
> ______________________________________________
> 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.
