[R] documentation of intersect() on string vector and num vector and on duplicated elements

Erik Iverson eiverson at NMDP.ORG
Wed Dec 2 22:48:03 CET 2009

> > intersect(c(1,3,2),c('1','3'))
> [1] "1" "3"
> Apparently, intersect() treats num as string. But this is not
> documented in the help. Could somebody add it in the future version of
> R?

This is more a general coercion feature. For example 1 == "1", see ?Comparison. 

> Also according to the help, the argument should not have duplicated
> elements. 

I think this is just because these functions were written with sets in mind, which would not have duplicated values, thus the word "conceptually".  The duplicated elements are simply discarded. 

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