That's right, however the bquote construct may be useful when combining several conditions,
subset(foo, eval(bquote(.(mycond) & a < 5)) ) baptiste 2009/8/22 Vitalie S. <vitosm...@rambler.ru>: > On Fri, 21 Aug 2009 22:38:09 +0200, baptiste auguie > <baptiste.aug...@googlemail.com> wrote: > >> Try this, >> >> mystr <-"c==1" >> subset(foo, eval(parse(text = mystr)) ) >> >> library(fortunes) >> fortune("parse") # try several times >> >> # I prefer this, but there is probably a better way >> mycond<- quote(c==1) >> subset(foo, eval(bquote(.(mycond))) ) >> > or just > subset(foo, eval(mycond)) > >> HTH, >> >> baptiste >> >> 2009/8/21 Sebastien Bihorel <sebastien.biho...@cognigencorp.com>: >>> >>> Dear R-users, >>> >>> The following question bothered me for the whole afternoon: how can one >>> pass >>> a string as the conditioning argument to subset? I tried plain mystr, >>> eval(mystr), expression(mystr), etc... I don't to be able to find the >>> correct syntax >>> >>>> foo <- data.frame(a=1:10,b=10:1,c=rep(1:2,5)) >>>> mystr<-"c==1" >>>> subset(foo,c==1) >>> >>> a b c >>> 1 1 10 1 >>> 3 3 8 1 >>> 5 5 6 1 >>> 7 7 4 1 >>> 9 9 2 1 >>>> >>>> subset(foo,mystr) >>> >>> Error in subset.data.frame(foo, mystr) : >>> 'subset' must evaluate to logical >>> >>> >>> >>> Any help would be greatly appreciated. >>> >>> Sebastien >>> >>> ______________________________________________ >>> 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. >>> >> >> >> > > > -- > Using Opera's revolutionary e-mail client: http://www.opera.com/mail/ > -- _____________________________ Baptiste Auguié School of Physics University of Exeter Stocker Road, Exeter, Devon, EX4 4QL, UK http://newton.ex.ac.uk/research/emag ______________________________________________ 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.