I would say this is not an error, but I think what you wrote isn't what you intended to do anyway.
y[1] is a data.frame which contains only the first column of y, which you assign to x$C, so now x$C is a data.frame. R allows data.frame to be plain vectors as well as matrices and data.frames, basically anything as long as it has the correct length or nrow. When the data.frame is formatted for printing, each column C is formatted then column-bound into another data.frame using as.data.frame.list, so it takes the name A because that's the name of the column from y. I think what you meant to do is x$C <- y[[1]] ## double brackets instead of single On Thu, Oct 26, 2023 at 4:14 AM Christian Asseburg <rh...@moin.fi> wrote: > > Hi! I came across this unexpected behaviour in R. First I thought it was a > bug in the assignment operator <- but now I think it's maybe a bug in the way > data frames are being printed. What do you think? > > Using R 4.3.1: > > > x <- data.frame(A = 1, B = 2, C = 3) > > y <- data.frame(A = 1) > > x > A B C > 1 1 2 3 > > x$B <- y$A # works as expected > > x > A B C > 1 1 1 3 > > x$C <- y[1] # makes C disappear > > x > A B A > 1 1 1 1 > > str(x) > 'data.frame': 1 obs. of 3 variables: > $ A: num 1 > $ B: num 1 > $ C:'data.frame': 1 obs. of 1 variable: > ..$ A: num 1 > > Why does the print(x) not show "C" as the name of the third element? I did > mess up the data frame (and this was a mistake on my part), but finding the > bug was harder because print(x) didn't show the C any longer. > > Thanks. With best wishes - > > . . . Christian > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
