[Octave-bug-tracker] [bug #56851] butter returns incorrect value

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?56851>

                 Summary: butter returns incorrect value 
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Mon 02 Sep 2019 06:08:21 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: hjborsje
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 5.1.0
        Operating System: Microsoft Windows

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Details:

>> [b,a] = butter (5,1/28800)
b =

 Columns 1 through 4:

   4.825699732353868e-22   2.412849866176934e-21   4.825699732353867e-21  
4.825699732353867e-21

 Columns 5 and 6:

   2.412849866176934e-21   4.825699732353868e-22

a =

 Columns 1 through 4:

   1.000000000000000e+00  -4.999646999743641e+00   9.998588061278351e+00 
-9.997882185366413e+00

 Columns 5 and 6:

   4.998588185872336e+00  -9.996470620406335e-01>>

>> [sum(a) sum(b)]
ans =

   0.000000000000000e+00   1.544223914353238e-20


MATLAB returns the value 5.5511e-16 for sum(a) and 8.88178e-16 for sum(b)




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