spanplus - sum of subspaces
computes a basis X such that:
the first dima columns of X span Range(A) and the following (dim-dima) columns make a basis of A+B relative to A.
The dim first columns of X make a basis for A+B.
One has the following canonical form for [A,B]:
[*,*] (dima rows) X'*[A,B]=[0,*] (dim-dima rows) [0,0]
tol is an optional argument (see function code).
A=rand(6,2)*rand(2,5); // rank(A)=2 B=[A(:,1),rand(6,2)]*rand(3,3); //two additional independent vectors [X,dim,dimA]=spanplus(A,B); dimA dim