Yes. paste0() can work on vectors. So paste0(mat[, col1], mat[, col2]) ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance Kliniekstraat 25 1070 Anderlecht Belgium
To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher The plural of anecdote is not data. ~ Roger Brinner The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. ~ John Tukey 2015-07-21 15:21 GMT+02:00 Emmanuel Levy <emmanuel.l...@gmail.com>: > Hi, > > The answer to this is probably straightforward, I have a dataframe and I'd > like to build an index of column combinations, e.g. > > col1 col2 --> col3 (the index I need) > A 1 1 > A 1 1 > A 2 2 > B 1 3 > B 2 4 > B 2 4 > > > At the moment I use: > col3 <- apply(mat[,sel.col], 1, paste0) > > But I wonder if another approach could be faster? > > Thanks, > > Emmanuel > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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 -- To UNSUBSCRIBE and more, see 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.
