column compression, kernel, nullspace
[W,rk]=colcomp(A [,flag] [,tol])
:A real or complex matrix : :flag character string : :tol real number : :W square non-singular matrix (change of basis) : :rk integer (rank of A) :
Column compression of A: Ac = A*W is column compressed i.e
Ac=[0,Af] with Af full column rank, rank( Af) = rank( A) = rk.
flag and tol are optional parameters: flag = ‘qr’ or ‘svd’ (default is ‘svd’).
tol = tolerance parameter (of order %eps as default value).
The ma-rk first columns of W span the kernel of A when size(A)=(na,ma)
A=`rand`_(5,2)*`rand`_(2,5);
[X,r]=colcomp(A);
`norm`_(A*X(:,1:$-r),1)