you need to use quotes, i.e., a[a$y > 0.5, "y"] <- 1
you can also use a$y[a$y > 0.5] <- 1 I hope it helps. Best, Dimitris ---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://med.kuleuven.be/biostat/ http://www.student.kuleuven.be/~m0390867/dimitris.htm ----- Original Message ----- From: "Sander Oom" <[EMAIL PROTECTED]> To: <r-help@stat.math.ethz.ch> Sent: Friday, August 04, 2006 1:48 PM Subject: [R] Data frame referencing? > Dear R users, > > When you do: >> x <- rnorm(10) >> y <- rnorm(10) >> z <- rnorm(10) >> a <- data.frame(x,y,z) >> a$x > [1] 1.37821893 0.21152756 -0.55453182 -2.10426048 -0.08967880 > 0.03712110 > [7] -0.80592149 0.07413450 0.15557671 1.22165341 > > Why does this not work: >> a[a$y>0.5,y] <-1 > Error in "[<-.data.frame"(`*tmp*`, a$y > 0.5, y, value = 1) : > only 0's may be mixed with negative subscripts > > While this works: >> a[a$y>0.5,2] <-1 > >> a > x y z > 1 1.37821893 -1.0887363 1.7340522 > 2 0.21152756 -0.7256467 -1.3165373 > 3 -0.55453182 1.0000000 -2.1116072 > 4 -2.10426048 -0.4898596 -1.5863823 > 5 -0.08967880 1.0000000 -0.9139706 > 6 0.03712110 1.0000000 -1.3004970 > 7 -0.80592149 -0.7004193 -0.1958059 > 8 0.07413450 1.0000000 -1.3574303 > 9 0.15557671 -0.3335407 -2.1991236 > 10 1.22165341 1.0000000 -0.7576708 > > For a complex loop I would prefer to reference the right colomn by > name, > not by number! Now, when the colomns change, I need to check my code > to > make sure that the right colomns are referenced. > > Suggestions much appreciated! > > Thanks in advance, > > Sander. > > ______________________________________________ > R-help@stat.math.ethz.ch 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 ______________________________________________ R-help@stat.math.ethz.ch 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.