[bug #68531] mldivide for non-square matrix

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URL:=0A  <https://savannah.gnu.org/bugs/?68531>=0A=0A                 Summa=
ry: mldivide for non-square matrix=0A                   Group: GNU Octave=
=0A               Submitter: lt1234=0A               Submitted: Thu 16 Jul =
2026 03:51:33 PM UTC=0A                Category: Octave Function=0A        =
        Severity: 3 - Normal=0A                Priority: 5 - Normal=0A     =
         Item Group: Documentation=0A                  Status: None=0A     =
        Assigned to: None=0A         Originator Name: lt1234=0A        Orig=
inator Email:=0A             Open/Closed: Open=0A         Discussion Lock: =
Unlocked=0A                 Release: 11.1.0=0A        Operating System: Mic=
rosoft Windows=0A           Fixed Release: None=0A         Planned Release:=
 None=0A=0A=0A    _______________________________________________________=
=0A=0AFollow-up Comments:=0A=0A=0A-----------------------------------------=
--------------=0ADate: Thu 16 Jul 2026 03:51:33 PM UTC By: Liang Tang <lt12=
34>=0AI believe that this observation is well known.  But I could not ident=
ify any=0Adocument explicitly calls out the difference.  So I am using the =
bug report to=0Adocument.  Thanks. =0A=0AFor mldivide with a non-square mat=
rix, we have =0A=0AOctave =0AIf the system is not square, or if the coeffic=
ient matrix is=0Asingular, a minimum norm solution is computed.=0A=0AMatlab=
=0AIf A is a rectangular m-by-n matrix with m ~=3D n, and B is a matrix wit=
h m=0Arows, then A\B returns a least-squares solution to the system of equa=
tions=0AA*x=3D B. x may not be the minimum-norm solution.    =0A=0AExample:=
 =0AA =3D [1 2 0; 0 4 3];=0Ab =3D [8; 18];=0Ax =3D A\b=0A=0AOctave =0A   0.=
9180=0A   3.5410=0A   1.2787=0AMatlab (see online documentation)   =0A    0=
=0A    4.0000=0A    0.6667=0A    =0AMatlab lsqminnorm outputs the Octave so=
lution above.  (see matlab lsqminnorm=0Aonline documentation figure) =0AX =
=3D lsqminnorm(A,b)=0A=0A=0A=0A=0A=0A=0A=0A=0A    _________________________=
______________________________=0A=0AReply to this item at:=0A=0A  <https://=
savannah.gnu.org/bugs/?68531>=0A=0A________________________________________=
_______=0AMessage sent via Savannah=0Ahttps://savannah.gnu.org/=0A
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