Oh wow, I guess I get it! Thank you. It is pretty tricky but I saw that it works very fast.
On Wed, Jan 29, 2014 at 9:31 PM, Duncan Murdoch <murdoch.dun...@gmail.com>wrote: > On 14-01-29 6:41 AM, Bill wrote: > >> Hi. I saw this example and I cannot begin to figure out how it works. Can >> anyone give me an idea on this? >> >> n = 9e6 >> df = data.frame(values = rnorm(n), >> ID = rep(LETTERS[1:3], each = n/3), >> stringsAsFactors = FALSE) >> >>> head(df) >>> >> values ID >> 1 -0.7355823 A >> 2 -0.4729925 A >> 3 -0.7417259 A >> 4 1.7633367 A >> 5 -0.3006790 A >> 6 0.6785947 A >> >> >> The idea is to replace all occurrences of A by 'Text for A'. >> >> He does this: >> >> translator_vector = c(A = 'Text for A', >> B = 'Text for B', >> C = 'Text for C') >> >> and subset this vector using df$ID: >> >> dum_vectorized = translator_vector[df$ID] >> >> It works but I have no idea why. >> > > He is indexing by name. The translator_vector looks like this: > > A B C > "Text for A" "Text for B" "Text for C" > > The first element is named A, the second B, the third C. > > So translator_vector["A"] is the same as translator_vector[1]. The ID > column in your dataframe is a vector of strings to be used as names, so > each one pulls out one element from the translator_vector. > > Duncan Murdoch > > > >> Thank you. >> >> [[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. >> >> > [[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.
