[Rd] ?mean

Martin Maechler maechler at stat.math.ethz.ch
Thu Jan 25 17:48:32 CET 2007

>>>>> "Gabor" == Gabor Grothendieck <ggrothendieck at gmail.com>
>>>>>     on Thu, 25 Jan 2007 09:53:49 -0500 writes:

    Gabor> The help page for mean does not say what happens when one
    Gabor> applies mean to a matrix.

    Gabor> mean and sd work in an inconsistent way on a matrix
    Gabor> so that should at least be documented.

You are right (though I think this *was* documented at some
point in time).

As a matter of fact, I hate the the inconsistencies you've
been mentioning, and I think is very wrong from an S-pedagogical
point of view.... both 
that    sd(mat)  :<==> apply(mat, 2, sd)
and   mean(dfr)  :<==> apply(dfr, 2, mean)
and it leads just to wrong ``analogy conclusions'' by useRs.

I'd vote for deprecating these ``builtin conveniences''
in order to gain consistency and clarity...

Though I haven't checked how many CRAN + Bioconductor packages
would break if we'd disactivate these two mis-features ...


    Gabor> Also there should be a See Also to colMeans since that
    Gabor> provides the missing column-wise analog to sd.

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