On 04 Aug 2015, at 10:50 , Karl Schilling <karl.schill...@uni-bonn.de> wrote:
> Dear All, > > I have an observation / question about how the function length() works once > package dplyr is loaded. > > Say we have a data.frame df with n rows and m columns. Then a way to get the > number of rows is to use > > length(df$m1) (m1 here stand is as the header of the first column) > > or, alternatively > > length(df[,1]). > > Both commands will return n. > > However, once dplyr is loaded, > > length(df[,1]) will return a value of 1. > > length(df$m1) and also length(df[[1]]) will correctly return n. > > I know that using length() may not be the most elegant or efficient way to > get the value of n. However, what puzzles (and somewhat disturbs) me is that > loading of dplyr affects how length() works, without there being a warning or > masking message upon loading it. > > Any clarification or comment would be welcome. Presumably, dplyr changes how [.data.frame works (by altering the default for drop=, I expect) so that df[,1] is a data frame with 1 variable and not a vector. And yes, that _is_ somewhat disturbing. -pd > > Thank you so much, > > Karl > > > -- > Karl Schilling > > ______________________________________________ > 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. -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Office: A 4.23 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ 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.
