[Rd] inaccuracy in man page for duplicated() + anyDuplicated() not working with MARGIN=0
maechler at stat.math.ethz.ch
Thu Nov 17 12:20:21 CET 2011
> In man page for duplicated:
> ‘duplicated()’: For a vector input, a logical vector of the same
> length as ‘x’. For a data frame, a logical vector with one
> element for each row. For a matrix or array, a logical array with
> the same dimensions and dimnames.
> When 'x' is a matrix or array, the returned value is NOT a logical
> > m <- matrix(c(3,2,7,6,2,7), nrow=3)
> > m
> [,1] [,2]
> [1,] 3 6
> [2,] 2 2
> [3,] 7 7
> > duplicated(m)
>  FALSE FALSE FALSE
> Only if MARGIN=0 it seems:
> > duplicated(m, MARGIN=0)
> [,1] [,2]
> [1,] FALSE FALSE
> [2,] FALSE TRUE
> [3,] FALSE TRUE
Indeed. Thank you for pointing this out.
I'll definitely fix that part of the help file.
> Also, any reason why this doesn't work?
> > anyDuplicated(m, MARGIN=0)
> Error in dim(newX) <- c(prod(d.call), d2) :
> dims [product 1] do not match the length of object 
well, because the R core colleague enhanced duplicated.array()
to work with MARGIN 0 (and similar cases) did not
update the parallel code in anyDuplicated.array() correspondingly.
> May be it could be equivalent to:
> > anyDuplicated(as.vector(m))
>  5
Yes, that's what will happen after I've committed my fixes.
Thank you very much, Hervé!
> Hervé Pagès
(*) having authored anyDuplicated()
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