Angle between two subspaces.

  SUBSPACE(A,B) finds the angle between two subspaces specified

  by the columns of A and B.  If A and B are vectors of unit

  length, this is the same as ACOS2C4HQXR(A'*B).

  If the angle is small, the two spaces are nearly linearly

  dependent.  In a physical experiment described by some

  observations A, and a second realization of the experiment

  described by B, SUBSPACE(A,B) gives a measure of the amount

  of new information afforded by the second experiment not

  associated with statistical errors of fluctuations.