Well, you won't like this, but it is kind of wimpily (is that a word?) documented:
If you check the code of factor(), you will see that nmax appears as an argument in a call to unique(). ?unique says for nmax, "... see duplicated" . And ?duplicated says: "If nmax is set too small there is liable to be an error: nmax = 1 is silently ignored." So sometimes you get an error when nmax is too small with the hash table error message; and sometimes you just apparently get the nmax argument ignored: > identical(factor(letters,nmax = 25), factor(letters,nmax=26)) [1] TRUE and that, to paraphrase what Roger Hammerstein said about Kansas City, is about "as fer as I can go." (http://lyricsplayground.com/alpha/songs/e/everythingsuptodateinkansascity.shtml) Cheers, Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) On Sat, Jun 3, 2017 at 6:14 PM, Ramnik Bansal <ramnik.ban...@gmail.com> wrote: > I have been trying to understand how the argument 'nmax' works in > 'factor' function. R-Documentation states - "Since factors typically > have quite a small number of levels, for large vectors x it is helpful > to supply nmax as an upper bound on the number of unique values." > > In the code below what is the reason for error when value of nmax is > 24. Why did the same error not occur with nmax = 25 and also how come > there are 26 levels when nmax = 25 ? > >> factor(x = letters, nmax = 26) > [1] a b c d e f g h i j k l m n o p q r s t u v w x y z > Levels: a b c d e f g h i j k l m n o p q r s t u v w x y z > >> factor(x = letters, nmax = 25) > [1] a b c d e f g h i j k l m n o p q r s t u v w x y z > Levels: a b c d e f g h i j k l m n o p q r s t u v w x y z > >> factor(x = letters, nmax = 24) > Error in unique.default(x, nmax = nmax) : hash table is full > > ______________________________________________ > 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.
