[Octave-bug-tracker] [bug #56582] [octave forge] (optim) lsqlin produces unexpected error on linearly dependent inputs

[Nicholas Jankowski]

URL:
  <https://savannah.gnu.org/bugs/?56582>

                 Summary: [octave forge] (optim) lsqlin produces unexpected
error on linearly dependent inputs
                 Project: GNU Octave
            Submitted by: nrjank
            Submitted on: Fri 05 Jul 2019 08:16:05 PM UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Unexpected Error
                  Status: None
             Assigned to: None
         Originator Name: Nicholas Jankowski
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 5.1.0
        Operating System: Any

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Details:

from a mailing list discussion [1]:

Octave:

C=[1 2 3;4 5 6; 2 4 6]
D=[4 5 8]'
lsqlin(C,D,[],[])
error: __qp__: operator *: nonconformant arguments (op1 is 2x2, op2 is 3x1)
error: called from
    quadprog at line 351 column 32
    lsqlin at line 123 column 19


Matlab:

>> C = [1 2 3;4 5 6; 2 4 6];

>> D=[4 5 8]';

>> lsqlin(C,D,[],[])
ans =
   NaN
   NaN
   NaN



the error seems to be related to the 1st and 3rd row of C being linearly
dependent. 


another possibly related error output:

Octave:

C=[1 2 3;4 5 6]
D=[4   5]'
A=[1 1 1;2 2 2]
B=[1 2]'

lsqlin(C,D,[],[],A,B,[],[])
error: quadprog: equality constraint matrix must be full row rank
error: called from
    quadprog at line 282 column 11
    lsqlin at line 123 column 19


Haven't checked that output in Matlab.   In any case, mailing list suggestion
is that Octave produces the NaN output like matlab rather than erroring out. 
Also was suggested having an option where lsqlin removes the linearly
dependent input for you, although no basis or approach for this to be done
consistently and compatibly has been discussed.


[1] http://octave.1599824.n4.nabble.com/lsqlin-error-message-tp4693279.html




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