[Octave-bug-tracker] [bug #45387] Matrix Product treats NaN times zero as zero

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?45387>

                 Summary: Matrix Product treats NaN times zero as zero
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Tue 23 Jun 2015 08:44:35 PM UTC
                Category: Interpreter
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Pete
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.0.0
        Operating System: GNU/Linux

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Details:

Start with this


x1 = [NaN, 2]
y = [0;1]
r1 = x1*y


Result is correct 
r1 = NaN

But, if we instead use

x2 = [NaN, 2;1,1]
y = [0;1]
r2 = x2*y


The result is
    r2 = [2;1]
which seems wrong (or at least inconsistent with result r1). I would have
expected
    r2 = [NaN;1]
which is what Matlab produces.

To summarize,
    x1*y = NaN times 0 plus 2 times 1 = NaN
but
    x2*y = [NaN times 0 + 2 times 1; 1 times 0 + 1 times 1] 
            = [2;1] 
instead of [NaN;1].






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