Thomas Lumley wrote: > On Fri, 29 May 2009, Jason Vertrees wrote: > >> My question is: why does the paradigm of changing the type of a 1D >> return value to an unlisted array exist? This introduces boundary >> conditions where none need exist, thus making the coding harder and >> confusing. >> >> For example, consider: >> > d = data.frame(a=rnorm(10), b=rnorm(10)); >> > typeof(d); # OK; >> > typeof(d[,1]); # Unexpected; >> > typeof(d[,1,drop=F]); # Oh, now I see. > > It does make it harder for programmers, but it makes it easier for > non-programmers. In particular, it is convenient to be able to do > d[1,1] to extract a number from a matrix, rather than having to > explicitly coerce the result to stop it being a matrix. > > At least the last two times this was discussed, there ended up being a > reasonable level of agreement that if someone's life had to be made > harder the programmers were better able to cope and that dropping > dimensions was preferable. > > -thomas > > Thomas Lumley Assoc. Professor, Biostatistics > tlum...@u.washington.edu University of Washington, Seattle
Thomas, Thanks for the quick response. I agree that extracting a number from a matrix/frame should result in a number not a matrix/frame. But, why do that for a 1D array of numbers? In my example, > d[,1]; is an array, not a single number. How does that help the novice user? I guess I just don't like the idea that the default result is to act unexpectedly and that a flag or boundary-conditional code is needed to "do the right thing". Regardless that's how it is, so I just need to learn the pitfalls for where that occurs. Thanks again, -- Jason -- Jason Vertrees, PhD Dartmouth College : j...@cs.dartmouth.edu Boston University : jas...@bu.edu PyMOLWiki : http://www.pymolwiki.org/ ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
