You may want to read the help page for '[' and '[[' a few more times (the differencese can be subtle).
The '[[' only returns a single element from a data structure (but in the case of a list, that single element can be quite complex). So something like list[[1:2]] does not make sense because you are asking something that returns 1 thing to return 2. You can do list[1:2] which will return a list consisting of the 1st 2 elements of the original list. If you list happens to be a data frame as well, then you can subset it like a matrix: mydf[1:2, 3:4] gives the 1st 2 rows of columns 3 and 4, mydf[,1:2] gives the first 2 columns. These will continue to be data frames (since '[' returns the same type of object), but tools like as.matrix can convert this into a matrix. -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare [EMAIL PROTECTED] (801) 408-8111 > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Olivier Lefevre > Sent: Thursday, April 24, 2008 4:16 PM > To: [EMAIL PROTECTED] > Subject: Re: [R] matrix from list > > Yes, unlist is the magic wand I was looking for. Thanks a million! > > Having said that, I find it rather arbitrary that you can > write mat[1:4] but not list[[1:2]]; IMO there should be no > need for a "magic" operator like unlist: > list[[1:length(list)]] could do the job. > > -- O.L. > > ______________________________________________ > 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.
