On Aug 3, 2010, at 7:59 PM, Johann Hibschman wrote: > Duncan Murdoch <murdoch.dun...@gmail.com> writes: >> On 29/07/2010 6:18 PM, chipmaney wrote: >>> >>> -Why does R recognize '[' as a function? >> >> Because it is a function. > > More explicitly, '[' is a string. sapply then calls match.fun to look > up that string to get the function named '['. > >>> -Why does it need the quotes? >> >> Because sapply(example,[,1) would not be syntactically valid. > > And, luckily enough, sapply uses the match.fun machinery to allow string > names for functions. This is also useful to ensure late binding of > functions in other contexts.
Also note the `[` (backtick) notation, which avoids using string names for non-syntactic names. (This was a relatively late (2003) addition to the R language, introduced to handle situations where strings would not substitute for function names. The older option of using strings for functions was retained for compatibility.) -- Peter Dalgaard Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ 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.
