Thanks Thierry, you made my day :)
On 21 July 2015 at 17:00, Thierry Onkelinx <thierry.onkel...@inbo.be> wrote: > Please always keep the mailing list in cc. > > If mat is a data.frame, then you can use do.call. Then the number of > columns doesn't matter. > > do.call(paste, mtcars[, c("mpg", "cyl")]) > do.call(paste, mtcars[, c("mpg", "cyl", "disp")]) > do.call(paste, mtcars) > > > 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 15:43 GMT+02:00 Emmanuel Levy <emmanuel.l...@gmail.com>: > >> Thanks! -- this is indeed much faster (plus I made a mistake, one has to >> use paste with the option collapse="". >> >> The thing is I'm looking for a solution *without paste*. The reason is >> that* there may be two or more columns*. >> >> >> >> On 21 July 2015 at 16:32, Thierry Onkelinx <thierry.onkel...@inbo.be> >> wrote: >> >>> 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.