On Mon, Apr 30, 2012 at 7:24 AM, steven_ew
<address@hidden> wrote:
Hi
I am new to Octave but quite experience in Matlab. I am trying to get a
script to run that creates and applies a Butterworth filter (it is a script
I have used lots in Matlab).
The key lines are :
bandHz = [100 500];
sampleFreq = 1001;
nyquistFreq = 0.5 * sampleFreq;
w = bandHz / nyquistFreq;
[z,p,k] = butter(2, w);
[sos,g] = zp2sos(z,p,k);
However, when Octave gets to zp2sos it gives this error:
error: cplxpair: could not pair all complex numbers
error: called from:
error: /usr/local/share/octave/3.6.1/m/general/cplxpair.m at line 126,
column 9
error: /home/steven/octave/signal-1.1.2/cplxreal.m at line 53, column 7
error: /home/steven/octave/signal-1.1.2/zp2sos.m at line 70, column 10
I wondered if someone could help me go about fixing this problem or give
some hint about where to start?
Thank you in advance for your help
Steven
Confirmed, I get the same error message.
The problem is that you are asking for a band pass filter and trying to do it with a second order filter.
Try a 4th order filter.
[z,p,k] = butter(4, w);
Doug