Re: Null Space

On Mar 30, 7:53 am, spellu...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
(Peter Spellucci) wrote:
In article <1175222437.274978.48...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, mich...@xxxxxxxxxxxxxxxx writes:

>Given a matrix A(m,n) where m<=n, LAPACK subroutine DGELQF calculates
>the LQ decomposition A=(L 0)Q where L(m,m) and Q(n,n). The subroutine
>DORGLQ forms the first m rows of the matrix Q. These rows correspond
>to the Transpose(Range) space of the matrix A. The null space
>transpose corresponds to the n-m rows of Q. Does anyone know of an
>efficient way to form this null space?
>
>Michael
>

use dormlq with the matrix to be multiplied defined as the last n-m columns of
the unit matrix since the null space of A is given by the last n-m columns
of Q' .
hth
peter

thanks peter

michael

.