Hello Germán. You probably want something like: sapply(vmat, function(curMat){ curMat[,999] != 0 }) Or if you want the indices, just surround this with a which.
HTH. Nick Sabbe -- ping: nick.sa...@ugent.be link: http://biomath.ugent.be wink: A1.056, Coupure Links 653, 9000 Gent ring: 09/264.59.36 -- Do Not Disapprove -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Germán Sanchis Sent: woensdag 8 december 2010 11:50 To: r-help@r-project.org Subject: [R] problem accessing complex list data frames Hi all. I am currently attempting to build a list of sparse matrixes. That I have already achieved, by > vmat <- list() > for (i in 1:n) { > vmat <- c(vmat, sparseMatrix(i,j,x=data) } How I am trying to select those elements from the list where the column e.g. 999 is not null. I can do this for one of the sparse matrices with > which(vmat[[1]][,999] != 0) which returns the rows where such column is non-zero. However, my purpose is to obtain the list indices of the sparse matrices with such non-zero elements. I tried things like which(vmat[[]][,999] != 0) which(vmat[,,999] != 0) sapply(vmat, which, [,999] != 0) but none worked... any help will be appreciated!! Cheers, German [[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.