On 07/08/2014, 4:51 AM, Martin Maechler wrote:
> This is not at all something new(*). As maintainer of the
> Matrix package, I don't like this inconsistency of base R's diag().
> We have had the following -- forever, almost surely inherited
> from S and S+ :
>
> diag(x) preserves the storage mode of x for 'complex' and
> 'double' precision, but converts integer and logicals to double :
>
> > storage.mode(x <- 1i + 1:7); storage.mode(diag(x))
> [1] "complex"
> [1] "complex"
> > storage.mode(x <- 0 + 1:7); storage.mode(diag(x))
> [1] "double"
> [1] "double"
>
> > storage.mode(x <- 1:7); storage.mode(diag(x))
> [1] "integer"
> [1] "double"
> > storage.mode(x <- 1:7 > 3); storage.mode(diag(x))
> [1] "logical"
> [1] "double"
>
> and so it is actually a bit cumbersome (and a memory waste in
> the case of large matrices) to create a diagonal integer or
> logical matrix.
>
> The help page does not mention the current behavior, though you
> may say it alludes to the fact that logicals are treated as 0/1
> implicitly (**)
>
I think the change to preserve integer makes sense, but preserving
logical does not. A diagonal matrix has zeros off the diagonal, and
they are not logical. Having diag() sometimes return a matrix with
FALSE off the diagonal just looks wrong.
Duncan Murdoch
> If I change this behavior such that logical and integer x are
> preserved,
>
> make check-all
>
> which includes all checks, including those of all recommended
> packages (including Matrix!) successfully runs through; so at
> least base + Recommended R never relies on the current
> behavior, nor should any "well programmed" R code ...
>
> Hence my proposal, somewhat tentative for now,
> to change this diag(.) behavior.
>
> Martin Maechler
>
> *) and possibly something we "can not" change in R, because too
> much code implicitely may be depending on it, but now I hope
> we can still...
>
> **) BTW, also including the somewhat amusing case of diag(c("A","B")).
>
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