On 19/03/2012 17:01, Terry Therneau wrote:
R version 2.14.0, started with --vanilla
> table(c(1,2,3,4,NA), exclude=2, useNA='ifany')
1 3 4 <NA>
1 1 1 2
This came from a local user who wanted to remove one particular response
from some tables, but also wants to have NA always reported for data
checking purposes.
I don't think the above is what anyone would want.
You have not told us what you want!
Try
> table(as.factor(c(1,2,3,4,NA)), exclude=2, useNA='ifany')
1 3 4 <NA>
1 1 1 1
Note carefully how 'exclude' is defined:
exclude: levels to remove from all factors in ‘...’. If set to ‘NULL’,
it implies ‘useNA="always"’.
As you did not specify a factor, 'exclude' was used in forming the 'levels'.
PS.
This is on a background of our local desires, which is to have the
default action of the table command be
to report NA, if present. (It's one of the only commands that we
globally override at Mayo.) The user had
added only the exclude=2 argument, and the useNA value is our default.
The above makes this harder to do without rewriting the command
wholesale, which is ok (we've done it before at
various times in R and Splus) but we would avoid it if possible. Please
no wars about whether this is the "right" decison or not, we've done it
for 10+ years and quite firmly believe the extra robustness gained by
having NA appear
is worth the maintainance bother, correctness being paramount in medical
research. We're not trying to convert anyone
else, just get feedback on the best way to approach this.
Most likely, feed table() a factor with the properties you want.
Terry T.
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Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
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