The documentation does say that the argument y must be in the domain of matrix inverse (%.). Matrix inverse accepts "tall" matrices and rejects "wide" matrices. (And of course accepts most square matrices.)
----- Original Message ----- From: "Leigh J. Halliwell" <[email protected]> Date: Monday, March 23, 2009 16:05 Subject: [Jprogramming] QR Decomposition To: 'Programming forum' <[email protected]> > Dear J Forum: > > I've been experimenting with 128!:0 (QR matrix decomposition) as > follows: > B =. |: A =. ? 4 7 $10 > $ each B;A > ----T---┐ > │7 4│4 7│ > L---+---- > $ each 128!:0 A > |length error > | $each 128!:0 A > $ each 128!:0 B > ----T---┐ > │7 4│4 4│ > L---+---- > > This suggests that the row dimension of the argument must be > greater than or > equal to the column dimension, and hence that T(Q) mmult Q is > the identity > matrix (orthogonal/Hermetian). If so, then noting this in > the Vocabulary > would be helpful. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
