[Rcpp-devel] setdiff

[Romain Francois]

Hello,

I've commited an initial version of setdiff.

There is room for improvement given the R version:

 > setdiff
function (x, y)
{
     x <- as.vector(x)
     y <- as.vector(y)
     unique(if (length(x) || length(y))
         x[match(x, y, 0L) == 0L]
     else x)
}

'initial' because it does not yet deal with missing values correctly.



Is the behavior of R's setdiff what we would want to reproduce:

 > setdiff( c(1), c(NA,1) )
numeric(0)

# that looks odd
 > setdiff( c(1), c(NA,2) )
[1] 1

# this too
 > setdiff( c(1,NA), c(1,2) )
[1] NA

# not sure what we should expect
 > setdiff( c(NA_integer_), c(NA_integer_) )
integer(0)



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Romain Francois
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