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[Octave-bug-tracker] [bug #40155] signal package: zp2sos return value is
From: |
Mike Miller |
Subject: |
[Octave-bug-tracker] [bug #40155] signal package: zp2sos return value is not compatible with Matlab |
Date: |
Wed, 09 Oct 2013 03:32:01 +0000 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.57 Safari/537.36 |
Update of bug #40155 (project octave):
Status: Need Info => Confirmed
Summary: Octave does not produce same results as Matlab for
iir scripts => signal package: zp2sos return value is not compatible with
Matlab
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Follow-up Comment #5:
I had someone run the following in Matlab:
N=7;
Wn=.4;
res='low';
[a,b]=butter(N,Wn,res)
[z,p,k]=butter(N,Wn,res)
sos=zp2sos(z,p,k)
[sos,g]=zp2sos(z,p,k)
Here are the results. As I suspected, the return value of zp2sos depends on
the number of output arguments. If the caller does not request the gain as a
separate value, it is incorporated into the sos array.
a =
0.0048 0.0339 0.1017 0.1695 0.1695 0.1017 0.0339
0.0048
b =
1.0000 -1.3893 1.6750 -1.0539 0.5086 -0.1448 0.0263
-0.0020
z =
-1
-1
-1
-1
-1
-1
-1
p =
0.2550 + 0.7653i
0.2550 - 0.7653i
0.1664 + 0.2222i
0.1664 - 0.2222i
0.1940 + 0.4668i
0.1940 - 0.4668i
0.1584
k =
0.0048
sos =
0.0048 0.0048 0 1.0000 -0.1584 0
1.0000 2.0000 1.0000 1.0000 -0.3328 0.0771
1.0000 2.0000 1.0000 1.0000 -0.3880 0.2555
1.0000 2.0000 1.0000 1.0000 -0.5101 0.6507
sos =
1.0000 1.0000 0 1.0000 -0.1584 0
1.0000 2.0000 1.0000 1.0000 -0.3328 0.0771
1.0000 2.0000 1.0000 1.0000 -0.3880 0.2555
1.0000 2.0000 1.0000 1.0000 -0.5101 0.6507
g =
0.0048
_______________________________________________________
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<http://savannah.gnu.org/bugs/?40155>
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