Hi!
I have large matrices, one column per variable and I have a vector of factors /
grouping symbols. Then I am computing subtotals for the groups but it takes
pretty long and thus I wanted to ask if there is a better way to do it or if
this is already the best way:
subTotals <- function(x, groupvec)
do.call("rbind",lapply(split(x,groupvec),colSums,na.rm=T))
Thanks reading my question and any hints!
Werner
---------------------------------
[[alternative HTML version deleted]]
On Fri, 12 May 2006, Werner Wernersen wrote:> Hi! > > I have large matrices, one column per variable and I have a vector of > factors / grouping symbols. Then I am computing subtotals for the groups > but it takes pretty long and thus I wanted to ask if there is a better > way to do it or if this is already the best way: subTotals <- > function(x, groupvec) > do.call("rbind",lapply(split(x,groupvec),colSums,na.rm=T))I suggest you look at rowsum (on a transpose of your matrix). It will not handle NAs, though, if you have any. -- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
Hi not sure about speed but aggregate can probably do it. aggregate(x, list(groupvec), sum, na.rm=T) HTH Petr On 12 May 2006 at 11:48, Werner Wernersen wrote: Date sent: Fri, 12 May 2006 11:48:45 +0200 (CEST) From: Werner Wernersen <pensterfuzzer at yahoo.de> To: r-help at stat.math.ethz.ch Subject: [R] optimal way to compute matrix subtotals?> Hi! > > I have large matrices, one column per variable and I have a vector of > factors / grouping symbols. Then I am computing subtotals for the > groups but it takes pretty long and thus I wanted to ask if there is a > better way to do it or if this is already the best way: subTotals <- > function(x, groupvec) > do.call("rbind",lapply(split(x,groupvec),colSums,na.rm=T)) > > > Thanks reading my question and any hints! > Werner > > > --------------------------------- > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.htmlPetr Pikal petr.pikal at precheza.cz
probably you want ?rowsum(); I hope it helps.
Best,
Dimitris
----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm
----- Original Message -----
From: "Werner Wernersen" <pensterfuzzer at yahoo.de>
To: <r-help at stat.math.ethz.ch>
Sent: Friday, May 12, 2006 11:48 AM
Subject: [R] optimal way to compute matrix subtotals?
> Hi!
>
> I have large matrices, one column per variable and I have a vector
> of factors / grouping symbols. Then I am computing subtotals for the
> groups but it takes pretty long and thus I wanted to ask if there is
> a better way to do it or if this is already the best way:
> subTotals <- function(x, groupvec)
> do.call("rbind",lapply(split(x,groupvec),colSums,na.rm=T))
>
>
> Thanks reading my question and any hints!
> Werner
>
>
> ---------------------------------
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>
Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm