Its been pointed out to me that the second one is wrong. It should be:
tail(this.matrix, -2)[, ncol(this.matrix)] which is not as compact as matlab or my prior post but still not particularly onerous. On Thu, Dec 11, 2008 at 11:49 PM, Gabor Grothendieck <ggrothendi...@gmail.com> wrote: > Use tail and head. See interspersed. > > On Thu, Dec 11, 2008 at 9:45 PM, Mike Rowe <mwr...@gmail.com> wrote: >> Greetings! >> >> I come to R by way of Matlab. One feature in Matlab I miss is its >> "end" keyword. When you put "end" inside an indexing expression, it >> is interpreted as the length of the variable along the dimension being >> indexed. For example, if the same feature were implemented in R: >> >> my.vector[5:end] > > tail(my.vector, -4) > >> >> would be equivalent to: >> >> my.vector[5:length(my.vector)] >> >> or: >> >> this.matrix[3:end,end] > > tail(tail(this.matrix, -2), 1) > >> >> would be equivalent to: >> >> this.matrix[3:nrow(this.matrix),ncol(this.matrix)] # or >> this.matrix[3:dim(this.matrix)[1],dim(this.matrix)[2]] >> >> As you can see, the R version requires more typing, and I am a lousy >> typist. >> >> With this in mind, I wanted to try to implement something like this in >> R. It seems like that in order to be able to do this, I would have to >> be able to access the parse tree of the expression currently being >> evaluated by the interpreter from within my End function-- is this >> possible? Since the "[" and "[[" operators are primitive I can't see >> their arguments via the call stack functions... >> >> Anyone got a workaround? Would anybody else like to see this feature >> added to R? >> >> Thanks, >> Mike >> >> ______________________________________________ >> 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. >> > ______________________________________________ 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.
