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Re: c2d is a Stub that only Produces Error Messages


From: Doug Stewart
Subject: Re: c2d is a Stub that only Produces Error Messages
Date: Tue, 22 Feb 2011 08:26:57 -0500




On Tue, Feb 22, 2011 at 7:33 AM, Lukas Reichlin <address@hidden> wrote:
On 22.02.2011, at 13:16, Doug Stewart wrote:

>
>
>
> On Tue, Feb 22, 2011 at 7:04 AM, Lukas Reichlin <address@hidden> wrote:
> On 22.02.2011, at 05:59, Thomas D. Dean wrote:
>
> > Octave 3.4.0, control 2.0.0
> >> From the Converting from S to Z domain thread,
> >
> > octave:1> num = [1 0];den = [1 0 4];
> > octave:2> sys = tf(num, den,1);sysz=c2d(sys,1);sysout(sysz,'tf')
> > error: tf: c2d: not implemented yet
> > error: called from:
> > error:   /home/tomdean/octave/control-2.0.0/@tf/__c2d__.m at line 31,
> >         column 7
> > error:   /home/tomdean/octave/control-2.0.0/@lti/c2d.m at line 46,
> >         column 7
> >
> > Looks like __c2d__ is a stub that only displays error messages, either
> > "not implemented" or "invalid method".
> >
> > # cat /home/tomdean/octave/control-2.0.0/@tf/__c2d__.m
> > ...<snip>
> > function sys = __c2d__ (sys, tsam, method = "zoh")
> >
> >  [p, m] = size (sys);
> >
> >  switch (method)
> >    case {"zoh", "std"}
> >      error ("tf: c2d: not implemented yet");
> >
> >    otherwise
> >      error ("tf: c2d: %s is an invalid method", method);
> >
> >  endswitch
> >
> > endfunction
> >
> > tomdean
>
> Yes, @tf/__c2d__.m is only a stub right now. address@hidden/__c2d__.m offers zero-order hold only.  There is a list of missing features in the PROJECTS file:
>
> http://octave.svn.sf.net/viewvc/octave/trunk/octave-forge/main/control/devel/PROJECTS
>
> Lukas
>
> _______________________________________________
> Help-octave mailing list
> address@hidden
> https://mailman.cae.wisc.edu/listinfo/help-octave
>
>
> Lukas , are you saying that c2d does not work any more???????
> Doug Stewart

Actually it never did for transfer functions. Internally, control-1.0.11 computed everything in state-space. As for now, you need to convert to state-space by  sys = ss (sys)  and discretize afterwards. Note that there is no d2c at all and that helping hands are always welcome ;-)

Regards,
Lukas


How does one revert to the old control tool box?
Doug

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