Thanks, it's interesting reading. I also noticed that
sw[, 1, drop = TRUE] is a vector (coerces to the lowest dimension) but sw[1, , drop = TRUE] is a one-row data frame (does not convert it into a list or vector) FS On 4/16/05, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > You should look at > > > ?"[" > > and look very carefully at the "drop" argument. For your example > > > sw[, 1] > > is the first component of the data frame, but > > > sw[, 1, drop = FALSE] > > is a data frame consisting of just the first component, as > mathematically fastidious people would expect. > > This is a convention, and like most arbitrary conventions it can be very > useful most of the time, but some of the time it can be a very nasty > trap. Caveat emptor. > > Bill Venables. > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Fernando Saldanha > Sent: Saturday, 16 April 2005 1:07 PM > To: Submissions to R help > Subject: [R] Getting subsets of a data frame > > I was reading in the Reference Manual about Extract.data.frame. > > There is a list of examples of expressions using [ and [[, with the > outcomes. I was puzzled by the fact that, if sw is a data frame, then > > sw[, 1:3] > > is also a data frame, > > but > > sw[, 1] > > is just a vector. > > Since R has no scalars, it must be the case that 1 and 1:1 are the same: > > > 1 == 1:1 > [1] TRUE > > Then why isn't sw[,1] = sw[, 1:1] a data frame? > > FS > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
