> I meant what is the design principle behind check.names being hardcoded to > FALSE. > I see no conflict with the purpose of cbind from the ability to specify > check.names > at the level of cbind.
One rationale is that data.frame(check.names=TRUE,...) does two things: it makes sure there are no duplicate names and it makes sure that all the names are syntactic names. If you have created a data.frame with non-syntactic names you would be annoyed if a call to cbind mangled its names, hence cbind.data.frame sets check.names=FALSE to avoid this. > d1 <- data.frame(`Mass (g)`=102, `Conc (% by vol.)`=0.23, check.names=FALSE) > d2 <- data.frame(`Accel (m/s/s)`=9.81, `Conc (% by vol.)`=0.23, check.names=FALSE) > names(d1) [1] "Mass (g)" "Conc (% by vol.)" > names(d2) [1] "Accel (m/s/s)" "Conc (% by vol.)" > names(data.frame(d1, d2, check.names=TRUE)) [1] "Mass..g." "Conc....by.vol.." "Accel..m.s.s." "Conc....by.vol...1" > names(data.frame(d1, d2, check.names=FALSE)) [1] "Mass (g)" "Conc (% by vol.)" "Accel (m/s/s)" "Conc (% by vol.)" > names(cbind(d1, d2)) [1] "Mass (g)" "Conc (% by vol.)" "Accel (m/s/s)" "Conc (% by vol.)" Perhaps data.frame() should throw an error if there are duplicate names, or perhaps it should have a separate argument to say what to do about duplicate names, but changing that sort of thing now would break a fair bit of code. Perhaps cbind.data.frame should not call data.frame, but copy the work that data.frame does or perhaps it should check for duplicate names on the output of data.frame(). Is it worth the time to do that? Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-devel-boun...@r-project.org [mailto:r-devel-boun...@r-project.org] On > Behalf > Of Fg Nu > Sent: Tuesday, July 23, 2013 10:48 AM > To: Ista Zahn > Cc: r-devel@r-project.org > Subject: Re: [Rd] cbind error with check.names > > > > > Is there then a reason that overriding the check.names default is forbidden > > from cbind? > I can't tell why this would be the case. > > For the same reason you can't have > > data.frame(x=1:10, x=11:20, check.names=TRUE, check.names=FALSE) > > or > > mean(x=1:10, x=11:20) > > i.e, you can't generally pass the same argument more than once. There > are exceptions to this, e.g., > > sum(c(NA, 1:10), na.rm=TRUE, na.rm=FALSE) > > but in general each argument can only be matched once. Since > cbind.data.frame calls data.frame with check.names=FALSE, you can't > supply it again. > > Best, > Ista > > > > > Thanks > > > > > > Yikes, no. As I mentioned to the SO poster, I get that bit. > > I meant what is the design principle behind check.names being hardcoded to > FALSE. I see > no conflict with the purpose of cbind from the ability to specify check.names > at the level > of cbind. > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
