Hi: On Thu, Jul 29, 2010 at 3:28 AM, pdb <ph...@philbrierley.com> wrote:
> > I've just tried to merge 2 data sets thinking they would only keep the > common > columns, but noticed the column count was not adding up. I've then > replicated a simple example and got the same thing happening. > > q1. why doesn't 'b' have a column name? > > q2. when I merge, why does the new column 'y' have all values as 5.1? > > Thanks in advance, > > Mr. confused > > > > a <- iris[,] > > b <- iris[,1] > b is not a data frame - since it is only one column, by default it is coerced into a numeric vector: > class(b) [1] "numeric" > b [1] 5.1 4.9 4.7 4.6 5.0 5.4 ... The way to keep b a data frame is to use the argument drop = FALSE, as in > b2 <- iris[, 1, drop = FALSE] # b2 is now a data frame > dd <- merge(iris, b2) > head(dd) Sepal.Length Sepal.Width Petal.Length Petal.Width Species 1 4.3 3.0 1.1 0.1 setosa 2 4.4 2.9 1.4 0.2 setosa 3 4.4 2.9 1.4 0.2 setosa 4 4.4 2.9 1.4 0.2 setosa 5 4.4 3.0 1.3 0.2 setosa 6 4.4 3.0 1.3 0.2 setosa HTH, Dennis > > > head(a) > Sepal.Length Sepal.Width Petal.Length Petal.Width Species > 1 5.1 3.5 1.4 0.2 setosa > 2 4.9 3.0 1.4 0.2 setosa > 3 4.7 3.2 1.3 0.2 setosa > 4 4.6 3.1 1.5 0.2 setosa > 5 5.0 3.6 1.4 0.2 setosa > 6 5.4 3.9 1.7 0.4 setosa > > head(b) > [1] 5.1 4.9 4.7 4.6 5.0 5.4 > > > > c <-merge(a,b) > > head(c) > Sepal.Length Sepal.Width Petal.Length Petal.Width Species y > 1 5.1 3.5 1.4 0.2 setosa 5.1 > 2 4.9 3.0 1.4 0.2 setosa 5.1 > 3 4.7 3.2 1.3 0.2 setosa 5.1 > 4 4.6 3.1 1.5 0.2 setosa 5.1 > 5 5.0 3.6 1.4 0.2 setosa 5.1 > 6 5.4 3.9 1.7 0.4 setosa 5.1 > > > > NCOL(a) > [1] 5 > > NCOL(b) > [1] 1 > > NCOL(c) > [1] 6 > > > > -- > View this message in context: > http://r.789695.n4.nabble.com/where-did-the-column-names-go-to-tp2306267p2306267.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. > [[alternative HTML version deleted]] ______________________________________________ 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.
