Try this: rowSums(rowsum(t(m), rep(1:3, c(2, 2, 1)), na.rm = TRUE))
On Fri, Jan 7, 2011 at 2:29 PM, emj83 <stp08...@shef.ac.uk> wrote: > > Hi, > > I would like to sum some specific columns in my matrix- for example, my > matrix looks like this: > [,1] [,2] [,3] [,4] [,5] > [1,] 1 NA NA NA NA > [2,] 2 1 NA 1 NA > [3,] 3 2 1 2 1 > [4,] 4 3 2 3 2 > [5,] NA NA NA 4 3 > [6,] NA NA NA 5 NA > > I would like to find the sum of the first two columns, the second two > columns and the last column: > i.e I am left with a vector of c(16, 18, 6). > > I know about colSums and sum overall- I just wondered if this type of > grouping can be included somehow in a vector such as c(2,2,1)? I don't > really want to have to use a loop for this. > > Many thanks Emma > -- > View this message in context: > http://r.789695.n4.nabble.com/Summing-over-specific-columns-in-a-matrix-tp3179400p3179400.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. > -- Henrique Dallazuanna Curitiba-Paraná-Brasil 25° 25' 40" S 49° 16' 22" O [[alternative HTML version deleted]]
______________________________________________ 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.
