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[matrix] Diff of /pkg/Matrix/TODO
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Diff of /pkg/Matrix/TODO

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revision 2571, Fri Jul 16 17:00:54 2010 UTC revision 2572, Sat Jul 17 16:54:41 2010 UTC
# Line 223  Line 223 
223  - sort(<sparseVector>, partial=..), needed, e.g. for mean(*, trim = .).  - sort(<sparseVector>, partial=..), needed, e.g. for mean(*, trim = .).
224    Note that defining xtfrm() does not "help" (as sort() then goes via dense    Note that defining xtfrm() does not "help" (as sort() then goes via dense
225    index).  See "mean" in R/Matrix.R    index).  See "mean" in R/Matrix.R
226    
227    - rcond(<sparseMatrix>) - for square currently goes via *dense* -- BAD --
228      can we go via qr() in any case?
229      In some cases, e.g. lmer()'s  "Lambda" (block triangular, small blocks)
230           rcond(L) :=  1 / (norm(L) * norm(solve(L)))
231      is simple {and remains sparse, as solve(L) is still block triangular}

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