D9a1 : Least squares ( $L_{2}$ ) solution

F04AMF	Least squares solution of $m$ real equations in $n$ unknowns, rank $= n$ , $m \geq n$ using iterative refinement (Black Box)
F04JGF	Least squares (if rank $= n$ ) or minimal least squares (if rank $< n$ ) solution of $m$ real equations in $n$ unknowns, $m \geq n$
F04QAF	Sparse linear least squares problem, $m$ real equations in $n$ unknowns
F04YAF	Covariance matrix for linear least squares problems, $m$ real equations in $n$ unknowns
F08AAF	Solves an overdetermined or underdetermined real linear system
F08ANF	Solves an overdetermined or underdetermined complex linear system
F08BAF	Computes the minimum-norm solution to a real linear least squares problem
F08BNF	Computes the minimum-norm solution to a complex linear least squares problem
F08KAF	Computes the minimum-norm solution to a real linear least squares problem using singular value decomposition
F08KCF	Computes the minimum-norm solution to a real linear least squares problem using singular value decomposition (divide-and-conquer)
F08KNF	Computes the minimum-norm solution to a complex linear least squares problem using singular value decomposition
F08KQF	Computes the minimum-norm solution to a complex linear least squares problem using singular value decomposition (divide-and-conquer)

D9a1 : Least squares (L2) solution