1.4.0: mean/sum of logicals

Torsten Hothorn <Torsten.Hothorn@rzmail.uni-erlangen.de> writes:

the NEWS file in  1.4.0-devel states:

o   mean() has `data frame' method applying mean column-by-column.
    When applied to non-numeric data mean() now returns NA rather
    than a confusing error message (for compatibility with S4).


which means:

R> mean(c(TRUE, FALSE))
[1] NA
Warning message:
argument is not numeric: returning NA in: mean.default(c(TRUE, FALSE))

but:

R> sum(c(TRUE, FALSE))
[1] 1

?sum states:

     sum(..., na.rm=FALSE)

Arguments:

     ...: numeric vectors.

and clearly

R> is.numeric(c(TRUE, FALSE))
[1] FALSE


this is confusing, isn't it? I think that `sum' and `mean' should take the
same arguments (and one probably will not allow to sum up logicals) or am
I missing something?

Torsten

Hmm. That slipped in without me noticing. Summing logicals is a fairly
common practice, as in

sem <- sd(x,na.rm=TRUE)/sqrt(sum(!is.na(x)))

Taking means of logicals is somewhat more rare, but it does work in
Splus 6.0 and it is a general rule coerce to logicals to 0/1, so I
suspect that this is just an oversight and we want mean.default to
start with

    if (!is.numeric(x) && !is.complex(x) && !is.logical(x)) {
        warning("argument is not numeric: returning NA")
        return(as.numeric(NA))

If Brian really meant otherwise, he'll explain why when he gets back
from Switzerland...

x <- c(TRUE, FALSE)
mean(x)

DF <- data.frame(x = x)
mean(DF$x)