It's certainly possible and I don't think you get any grueling inefficiencies. along the way.
Another way that might or might not make sense for you is to use a nifty trick I saw Gabor and Duncan M use a few weeks ago: you can give dimensionality to a list and then subset it in the "normal" ways: e.g., x <- list(a = 1, b = 2, c = 3, d = 4) dim(x) <- c(2,2) colnames(x) <- c("a", "b") x[2,] x[,2] x[[2]]] x[,"a"] Might be of help for some nifty indexing. (Or it might look so crazy to scare folks away: your call) Michael On Wed, Feb 22, 2012 at 10:17 AM, Stefano Sofia <stefano.so...@regione.marche.it> wrote: > Dear R users, > I have difficulty to create a list within a list. > Example: with > >> A <- vector(mode="list", 4) > > I create a list of 4 elements: >> A > [[1]] > NULL > > [[2]] > NULL > > [[3]] > NULL > > [[4]] > NULL > > In each element of this list I can store, for example, a matrix: > A[[1]] <- matrix ... > > I need each element of A to be a list (all the lists of the same length), and > then store matrices within these lists. > Have I explained it in a reasonable way? > Is it possible? > If yes, is it efficient? For my purposes, I need to have A a list of length > 20000 or 30000 (even 50000 possibily), and the lists within A of length 1000 > and store square matrices of dimension 13. > > Thank you for your attention and your help > Stefano Sofia PhD > > > > AVVISO IMPORTANTE: Questo messaggio di posta elettronica può contenere > informazioni confidenziali, pertanto è destinato solo a persone autorizzate > alla ricezione. I messaggi di posta elettronica per i client di Regione > Marche possono contenere informazioni confidenziali e con privilegi legali. > Se non si è il destinatario specificato, non leggere, copiare, inoltrare o > archiviare questo messaggio. Se si è ricevuto questo messaggio per errore, > inoltrarlo al mittente ed eliminarlo completamente dal sistema del proprio > computer. Ai sensi dell’art. 6 della DGR n. 1394/2008 si segnala che, in > caso di necessità ed urgenza, la risposta al presente messaggio di posta > elettronica può essere visionata da persone estranee al destinatario. > IMPORTANT NOTICE: This e-mail message is intended to be received only by > persons entitled to receive the confidential information it may contain. > E-mail messages to clients of Regione Marche may contain information that is > confidential and legally privileged. Please do not read, copy, forward, or > store this message unless you are an intended recipient of it. If you have > received this message in error, please forward it to the sender and delete it > completely from your computer system. > ______________________________________________ > 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.