R-alpha: bug in sum

[Andreas Weingessel]

If the sum of a vector containing NAs is computed and na.rm is FALSE,
the result is not always NA. 

R> w <- c(1:3,NA)
R> sum(w)
[1] NA

BUT

R> w <- c(NA, 1:3)
R> sum(w)
[1] 0

It seems that this problem only occurs, if the first element is NA.

Andreas

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