[Octave-bug-tracker] [bug #43947] TF function in Control returns different sized x.Num and x.Den if higher order coefficients missing

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?43947>

                 Summary: TF function in Control returns different sized x.Num
and x.Den if higher order coefficients missing
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Tue 06 Jan 2015 10:54:11 PM UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: Scott Jobling
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.8.2
        Operating System: Microsoft Windows

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Details:

I was running a script originally built for Matlab and ran into several
out-of-bounds errors when making assumptions about how many modeling
coefficients should be returned by the numerator/denominator calls. I believe
this is an issue with the x.Num/Den properties only returning the minimum
necessary coefficients from the control model parameters. The person that
wrote this for Matlab did so in the last two years, so I'm assuming the issues
is on the Octave end. So, via Octave's TF function:


% (2*s^2 + 1*s^1 + 0) / (3*s^3 + 2*s^2 + 1*s^1 + 0) 
x.Num % 2 1 0
x.Den % 3 2 1 0


Padding the smaller of the x.Num / x.Den returned arrays with zeros for the
missing coefficients fixed the problem for me.


num = x.Num;
num = padarray(num, [0 2], 'pre');
% num => 0 2 1 0 => same size as x.Den





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