On 15-08-2013, at 09:29, Zhang Weiwu <zhangwe...@realss.com> wrote: > When you select a single row from a matrix, the dimsion is lost: > >> n <- matrix(nrow = 3, ncol = 5) >> dim(n) > [1] 3 5 >> dim(n[1,]) > NULL >> dim(n[2,]) > NULL > > This doesn't happen if you select more than one row: > >> dim(n[1:2,]) > [1] 2 5 > > This is causing trouble. SCENARIO: when I filter out unqualified sampled > data, I was not unaware that only one row of data qualifies, and the resulted > selected data thus doesn't have dimension. I would call matrix[,3] and get > an error. > > One way to mend this is to re-assign the dimension to the result set, but > that destories column names... > >> selected = n[1,] >> selected > unixtime agio count ask bid > NA NA NA NA NA >> dim(selected) > NULL >> dim(selected) <- c(1,5) >> selected > [,1] [,2] [,3] [,4] [,5] > [1,] NA NA NA NA NA > > Is there a way to retain dimension when selecting only one row from a matrix?
See the examples in ?`[` (seventh one). n[1,,drop=FALSE] Berend ______________________________________________ R-help@r-project.org mailing list 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.
