probably you want something like the following: A[cbind(rep(1, length(x)), x, y)]
I hope it helps. Best, Dimitris ---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://med.kuleuven.be/biostat/ http://www.student.kuleuven.be/~m0390867/dimitris.htm ----- Original Message ----- From: "Demi Anderson" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, February 01, 2007 2:34 PM Subject: [R] Index mapping on arrays > Dear R-community, > > I have some trouble with index mappings for arrays. If, for example, > I have the array > > R> A <- array(1:9, c(3,3,2)) > > and two index mappings both of same size > > R> x <- c(2, 3) > R> y <- c(1, 2) > > Now I want to access the elements (A[1, x[i], y[i]])_i of A, i.e. > A[1, x[1], y[1]] = A[1, 2, 1] and A[1, x[2], y[2]] = A[1, 3, 2]. > > If I use > > R> A[1, x, y] > > I would get every combinations of indices of all elements of x and y > i.e. A[1, x[1], y[1]], A[1, x[1], y[2]], A[1, x[2], y[1]] and A[1, > x[2], y[2]]. But how can I access the elements (A[1, x[i], y[i]])_i. > My arrays dimensions are actually large in the second > component (for example the dimension might be 10*10000*10) so I'm > looking for a method avoiding loops. > > The question is probably trivial for you, but I just could not > figure it out. So sorry for bugging you and many thanks in advance > for any help. > > Best wishes, Demi Anderson. > -- > "Feel free" - 10 GB Mailbox, 100 FreeSMS/Monat ... > > ______________________________________________ > [email protected] 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. > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm ______________________________________________ [email protected] 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.
