Re: Null Space


In article <1175222437.274978.48150@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
michael@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

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