On Apr 15, 2010, at 8:37 AM, Wilmar Igl wrote:
Dear all,
just a stupid R question, since the results puzzle me a bit:
sum(c(NA,NA), na.rm=TRUE)
[1] 0
NA + NA
[1] NA
NA + 1
[1] NA
Why does sum(c(NA,NA), na.rm=TRUE) return 0 and not NA?
> sum(c())
[1] 0
?sum
"NB: the sum of an empty set is zero, by definition."
--
David Winsemius, MD
West Hartford, CT
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