On Aug 28, 2012, at 05:11 , David Winsemius wrote:
> That's exactly it. If a logical index returns NA, its row is included in the
> output of "[" extraction. You can correct what I consider a failing and
> others consider a feature with:
>
> df[df$Renewal==TRUE & !is.na(df$Renewal), 1:2]
>
Precisely. To elaborate, some consider it a feature because, if the condition
is NA, you effectively don't know whether to include or not, so it includes
with NA content, which is arguably a lesser loss of information.
Also, it treats numerical and logical NA on the same footing so that x[NA] is
the same as x[as.numeric(NA)]. It's awkward if x[NA] has length zero but
x[c(1,NA)] has length 2.
For integer NA, you definitely want not to exclude, consider plot(...,
col=c("red", "blue", "green")[g])
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd....@cbs.dk Priv: pda...@gmail.com
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