try this (use '[' for indexing) > jlist <- list(NULL,c(1,0),NULL,c(1,2,3), NULL) > jlist [[1]] NULL
[[2]] [1] 1 0 [[3]] NULL [[4]] [1] 1 2 3 [[5]] NULL > which(sapply(jlist, length) > 0) [1] 2 4 > jlist[sapply(jlist, length) > 0] [[1]] [1] 1 0 [[2]] [1] 1 2 3 > On Thu, Nov 8, 2012 at 9:42 AM, Gonçalo Ferraz <gferra...@gmail.com> wrote: > Hi, > > > If I have a vector: > > junk <- c(2,0,0,3,0) > > and want to access, say, all the elements that are greater than zero. I just > do: > > junk[which(junk>0)] > > > > Now, If I have a list: > > jlist <- list(NULL,c(1,0),NULL,c(1,2,3), NULL) > > and want to access all the elements that have length greater than zero, I > know how to find the elements with: > > which(sapply(jlist,length)>0) > > But how do I get a new list, only with the non-zero-length elements, without > having to write a for loop? > > I tried: > > notnull <- which(sapply(jlist,length)>0) > jlist[[notnull]] > > and got the error: > > Error in jlist[[notnull]] : recursive indexing failed at level 2 > > Thank you for any help! > > ______________________________________________ > 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. -- Jim Holtman Data Munger Guru What is the problem that you are trying to solve? Tell me what you want to do, not how you want to do it. ______________________________________________ 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.
