What do you think about this? apply(data, 3, '[', indices)
On Mon, Aug 1, 2011 at 4:38 AM, Jannis <bt_jan...@yahoo.de> wrote: > Dear R community, > > > I have a general question regarding indexing in multidiemensional arrays. > > Imagine I have a three dimensional array and I only want to extract on > vector along a single dimension from it: > > > data <- array(rnorm(64),dim=c(4,4,4)) > > result <- data[1,1,] > > If I want to extract more than one of these vectors, it would now really > help me to supply a logical matrix of the size of the first two dimensions: > > > indices <- matrix(FALSE,ncol=4,nrow=4) > indices[1,3] <- TRUE > indices[4,1] <- TRUE > > result <- data[indices,] > > This, however would give me an error. I am used to this kind of indexing > from Matlab and was wonderingt whether there exists an easy way to do this > in R without supplying complicated index matrices of all three dimensions or > logical vectors of the size of the whole matrix? > > The only way I could imagine would be to: > > result <- data[rep(as.vector(indices),**times=4)] > > but this seems rather complicated and also depends on the order of the > dimensions I want to extract. > > > I do not want R to copy Matlabs behaviour, I am just wondering whether I > missed one concept of indexing in R? > > > > Thanks a lot > Jannis > > ______________________________**________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help> > PLEASE do read the posting guide http://www.R-project.org/** > posting-guide.html <http://www.R-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. > [[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.
