For some reason I did not receive your email. Sorry for the inconvenience caused
________________________________ From: Dennis Murphy <djmu...@gmail.com> Cc: Rhelp <r-help@r-project.org> Sent: Wed, September 22, 2010 1:46:28 PM Subject: Re: [R] efficient list indexing Hi: I believe we had this discussion yesterday, http://r.789695.n4.nabble.com/Object-oriented-programming-in-R-td2538541.html#a2538916 but since you chose to repeat that message, it clearly wasn't enough, so start with http://cran.r-project.org/doc/manuals/R-intro.html#Lists http://stackoverflow.com/questions/2050790/how-to-correctly-use-lists-in-r With the following example as a reference: Empl <- list(employee = "Anna", spouse = "Fred", children = 3, child.ages = c(4, 7, 9)) we quote Venables and Ripley (2002, p. 45): "It is important to appreciate the difference between [ and [[. The [ form extracts sub-vectors, so Empl[2] is a list of length one, whereas Empl[[2]] is a component (a character vector of length one)." In that context, consider the following: > Empl$employee [1] "Anna" > Empl$child.ages[2] [1] 7 > x <- "spouse"; Empl[[x]] [1] "Fred" > Empl[[3]] [1] 3 > Empl[[4]] [1] 4 7 9 > Empl[[4]][2] [1] 7 > Empl[4] $child.ages [1] 4 7 9 > Empl[4][2] # Why? $<NA> NULL > Empl[2] $spouse [1] "Fred" > Empl[[2]] # Why the difference? [1] "Fred" A somewhat more expansive discussion is found on pp. 12-13 of Venables and Ripley (2000), S Programming. Dennis Hello everyone, > >I need some help with lists inside lists (a good way to emulate a struct)\ > >Assume that there is a small list called fred: >fred <- list(happy = 1:10, name = "squash") > > >and a big list called bigfred that includes fred list 5 times >bigfred <- rep(fred,5) > >Is it possible somehow to index all these sublists(fred) inside bigfred with a >more direct way like this: >bigfred[1] shows the first sublist fred >bigfred[2][2] shows the second sublist fred, the second element of the fred list > >So far I found some way to do this by refering to the sublists by the following: >bigfred[1+index*length(fred)] >where index shows the beginning of a sublist. > >I would like to thank you in advance for your help >Best Regards >Alex > > > > > [[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. > [[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.
