ken knoblauch <ken.knoblauch <at> inserm.fr> writes: > > Michael Bach <phaebz <at> gmail.com> writes: > > how do I e.g. square each second element of a > vector with an even > > number of elements? Or more generally to > apply a function to every > > 'nth' element of a vector. I looked into the > apply functions, but > > found no hint. > > For example: > > v <- c(1, 2, 3, 4) > > mysquare <- function (x) { return (x*x) } > > w <- applyfun(v, mysquare, 2) > > then w should be c(1, 4, 3, 16) > > Michael Bach > > Hi Michael, > > v^(2 - seq_along(v) %% 2) > > [1] 1 4 3 16 > > Ken > Actually, combining Ista and my responses, a general response could be something like
ifelse(v %% n, v, function(v){} ) where you have set n and define some function HTH, Ken -- Ken Knoblauch Inserm U846 Stem-cell and Brain Research Institute Department of Integrative Neurosciences 18 avenue du Doyen Lépine 69500 Bron France tel: +33 (0)4 72 91 34 77 fax: +33 (0)4 72 91 34 61 portable: +33 (0)6 84 10 64 10 http://www.sbri.fr/members/kenneth-knoblauch.html ______________________________________________ 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.