Exactly what I thought too the first time I read ?merge. R sometimes has its own approach.
John Kane Kingston ON Canada > -----Original Message----- > From: r-help@r-project.org > Sent: Mon, 1 Jun 2015 14:47:07 +0000 (UTC) > To: li...@dewey.myzen.co.uk, r-help@r-project.org > Subject: Re: [R] merge function > > I understood that by would take the intersection of names(x) and > names(y), names(x) being the column names of x and names(y), column names > of y. > if x has 5 col and the col names of x are col1, col2... col5 and y has 3 > col and their names are col1, col2, col3, I thought that the merged data > set will have 3 col, namely col1, col2, col3 but all 5 col, i.e. col1, > col2... col5 are taken if nothing is specified for the by arg. > Cheers, > > > > On Monday, June 1, 2015 4:32 PM, Michael Dewey > <li...@dewey.myzen.co.uk> wrote: > > > > > On 01/06/2015 14:46, carol white via R-help wrote: >> Hi,By default the merge function should take the intersection of column >> names > > (if this is understood from by = intersect(names(x), names(y)), > > Dear Carol > The by parameter specifies which columns are used to merge by. Did you > understand it to be which columns are retained in the result? > > Just a hunch, and if not then you need to give us a toy example. > > > > but it takes all columns. How to specify the intersection of column > names? > > Thanks >> Carol >> >> [[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. >> > > -- > Michael > http://www.dewey.myzen.co.uk/home.html > > > > [[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. ____________________________________________________________ FREE 3D MARINE AQUARIUM SCREENSAVER - Watch dolphins, sharks & orcas on your desktop! ______________________________________________ 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.
