[R] Schur decomposition?

[Douglas Bates]

Spencer Graves wrote:
>      Does R have a function for the Schur decomposition?  The 
> documentation for library(Matrix) describes a function "Schur", but it 
> seems to be missing from the Windows version 0.8-14 (2004-09-14) and 
> 0.8-15 (2004-10-02).
>      The R 2.0.0 pat documentation for "eigen" refers to 
> "http://www.netlib.org/lapack/lug/lapack_lug.html", and the description 
> there for eigen analysis of a non-symmetric matrix says, "This problem 
> can be solved via the Schur factorization of A, defined in the real case as
> A = ZTZT,
> 
> where Z is an orthogonal matrix and T is an upper quasi-triangular 
> matrix with 1-by-1 and 2-by-2 diagonal blocks, the 2-by-2 blocks 
> corresponding to complex conjugate pairs of eigenvalues of A."
>      Thanks,
>      Spencer Graves

That documentation entry was a note to myself to add the Schur 
factorization to the Matrix package but I have not yet done so.  If 
anyone can suggest a reasonable data structure for the result, it would 
be fairly easy to add the Schur decomposition.