attr(terms(formula), "response") is 1 if the formula has a left hand side and 0 otherwise.
At a lower level, you can look at length(formula): 2 means there is no LHS, 3 means there is (any other value indicates that someone made a call object that the parser would not make). Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of Erik Iverson > Sent: Monday, December 13, 2010 12:17 PM > To: R-help > Subject: [R] Does a formula object have a "left hand side" > > Hello, > > Does anyone know of a function that will determine whether > or not a formula object has a left hand side? > > I.e., can differentiate between > > y ~ x + z > > and > > ~ x + z > > Perhaps I'm overlooking the obvious... > > Thanks! > > ______________________________________________ > 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. > ______________________________________________ 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.
