On Sat, Aug 18, 2012 at 9:33 AM, Martin Maechler <maech...@stat.math.ethz.ch> wrote: >>>>>> Joshua Ulrich <josh.m.ulr...@gmail.com> >>>>>> on Sat, 18 Aug 2012 10:16:09 -0500 writes: > > > I don't know if this is better, but it's the most obvious/shortest I > > could come up with. Transpose the data.frame column to a 'row' vector > > and drop the dimensions. > > R> identical(nv, drop(t(df))) > > [1] TRUE > > Yes, that's definitely shorter, > congratulations! > > One gotta is that I'd want a solution that also works when the > df has more columns than just one... > > Your idea to use t(.) is nice and "perfect" insofar as it > coerces the data frame to a matrix, and that's really the clue: > > Where as df[,1] is losing the names, > the matrix indexing is not. > So your solution can be changed into > > t(df)[1,] > > which is even shorter... > and slightly less efficient, at least conceptually, than mine, which has > been > > as.matrix(df)[,1] > > Now, the remaining question is: Shouldn't there be something > more natural to achieve that? > (There is not, currently, AFAIK).
Perhaps a data frame method for as.vector? as.vector.data.frame <- function(x, ...) as.matrix(x)[,1] as.vector(df[1]) or an additional argument to `[.data.frame` like keep.names, which defaults to FALSE to maintain current behavior but can optionally be TRUE. Cheers, Josh > > Martin > > > > Best, > > -- > > Joshua Ulrich | about.me/joshuaulrich > > FOSS Trading | www.fosstrading.com > > > > On Sat, Aug 18, 2012 at 10:03 AM, Martin Maechler > > <maech...@stat.math.ethz.ch> wrote: > >> Today, I was looking for an elegant (and efficient) way to get a named > >> (atomic) vector by selecting one column of a data frame. Of course, > >> the vector names must be the rownames of the data frame. > >> > >> Ok, here is the quiz, I know one quite "cute"/"slick" answer, but was > >> wondering if there are obvious better ones, and also if this should > >> not become more idiomatic (hence "R-devel"): > >> > >> Consider this toy example, where the dataframe already has only one > >> column : > >> > >>> nv <- c(a=1, d=17, e=101); nv > >> a d e > >> 1 17 101 > >> > >>> df <- as.data.frame(cbind(VAR = nv)); df > >> VAR > >> a 1 > >> d 17 > >> e 101 > >> > >> Now how, can I get 'nv' back from 'df' ? I.e., how to get > >> > >>> identical(nv, .......) > >> [1] TRUE > >> > >> where ...... only uses 'df' (and no non-standard R packages)? > >> > >> As said, I know a simple solution (*), but I'm sure it is not > >> obvious to most R users and probably not even to the majority of > >> R-devel readers... OTOH, people like Bill Dunlap will not take > >> long to provide it or a better one. > >> > >> (*) In my solution, the above '.......' consists of 17 letters. > >> I'll post it later today (CEST time) ... or confirm > >> that someone else has done so. > >> > >> Martin > >> > >> ______________________________________________ > >> 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 -- Joshua Wiley Ph.D. Student, Health Psychology Programmer Analyst II, Statistical Consulting Group University of California, Los Angeles https://joshuawiley.com/ ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
