On 19 November 2011 23:58, Jerry <lancebo...@qwest.net> wrote: > Hi All, > > The function zp2sos in Signals always returns 1.0 for the gain of the second > order sections. This isn't very useful. I believe it should return the gain > factor to make the cascade of second order sections equal to the input filter > which is in the form [zeros poles gain]. Indeed, this is the behavior > described for the Matlab version at > http://www.mathworks.com/help/toolbox/signal/ref/zp2sos.html. > > An example that shows the problem is simply to convert a second order filter > in z-p-g form to a single second order section: > > octave-3.4.0:1> [b,a] = butter(2, 0.2) > b = > > 0.067455 0.134911 0.067455 > > a = > > 1.00000 -1.14298 0.41280 > > octave-3.4.0:2> [z, p, g] = butter(2, 0.2) > z = > > -1 -1 > > p = > > 0.57149 + 0.29360i 0.57149 - 0.29360i > > g = 0.067455 > octave-3.4.0:3> [sos, sos_g] = zp2sos(z', p') > sos = > e > 1.00000 2.00000 1.00000 1.00000 -1.14298 0.41280 > > sos_g = 1 >>>>> Should be 0.067455 <<<<<< > > > The filter from the first input line should be the same as from the last > input line but it differs in the gain factor. This is easy to fix but as it > is the user has to do it. > > On two related matters, the Octave documentation for zp2sos, > http://octave.sourceforge.net/signal/function/zp2sos.html, states that the > arguments to zp2sos should be column vectors but using either column or row > vectors results in the same answer. > > Also, on the same doc page, a quantity called Bscale is mentioned, but only > once; it does not reference anything on the page. This should also be fixed. > It probably refers to g but g is incorrect as noted above. > > I suppose the functions mentioned in the "See also" should be checked for > similar problems. > > Jerry
Hi Jerry, do you think you can submit a patch to fix these (or maybe just some) of the issues? Carnë ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d _______________________________________________ Octave-dev mailing list Octave-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/octave-dev
