question about setdiff()

`Same' object appearing more than once do not count, I guess.  As an
example:
setdiff(c(1,2,2), c(3,4))
[1] 1 2

The second `2' does not show up, because
setdiff
function (x, y) 
unique(if (length(x) || length(y)) x[match(x, y, 0) == 0] else x)
<environment: namespace:base>

Note the unique().

Andy
From: Svetlana Eden

Thank you for your answers,
I have another question:

the behaviour of setdiff(indicesFalse, indicesNA)
does not seem predictable to me.

indices
[1] 1 2 3 4 5 6
compareVector
[1]    NA  TRUE  TRUE  TRUE FALSE    NA
  indicesNA = indices[is.na(compareVector)]
  indicesNA
[1] 1 6
  indicesFalse = indices[compareVector == FALSE]
  indicesFalse
[1] NA  5 NA
  setdiff(indicesNA, indicesFalse) ######################## OK
[1] 1 6
  setdiff(indicesFalse, indicesNA) ######################## I would
  expect here 'NA 5 NA'
[1] NA  5

-- 
Svetlana Eden        Biostatistician II            School of Medicine
                     Department of Biostatistics   Vanderbilt 
University

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