[Rd] Suggestion: add a warning in the help-file of unique()
stigler3 at etu.unige.ch
Thu Apr 17 12:44:32 CEST 2008
I'm sorry if this suggestion/correction was already made but after a
search in devel list I did not find any mention of it.
I would just suggest to add a warning or an exemple for the help-file of
the function unique() like
"Note that unique() compares only identical values. Values which, are
printed equally but in facts are not identical will be treated as
> a<-c(0.2, 0.3, 0.2, 0.4-0.1)
 0.2 0.3 0.2 0.3
 0.2 0.3 0.3
Well this is just the idea and the sentence could be made better (my
poor english...). Maybe a reference to RFAQ 7.31 could be made.
Maybe is this behaviour clear and logical for experienced users, but I
don't think it is for beginners. I personnaly spent two hours to see
that the problem in my code came from this.
I was thinking about modify the function unique() to introduce a "tol"
argument which allows to compare with a tolerance level (with default
value zero to keep unique consistent) like all.equal(), but it seemed
too complicated with my little understanding.
Bests regards and many thanks for what you do for R!
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