Re: zp2sos error: cplxpair: could not pair all complex numbers

[Ozzy Lash]

On Fri, Jan 6, 2017 at 8:04 AM, Nicholas Jankowski <address@hidden> wrote:

again, no intuitive sense of what I'm looking at, but how important is
the sort order for sos? The values all seem the same out to 1E-14 or
so, but matlab seems to have them sorted differently.

Looking at the documentation for matlab, the zp2sos implementation has an "order" argument that can be either up or down.  The default is up, and in that case it orders the second order sections with the section that has poles furthest from the unit circle first.  I think this ordering is intended to reduce roundoff error, so it might be a good addition to the signal package to allow this argument.

See: https://www.mathworks.com/help/signal/ref/zp2sos.html

and: http://www.emba.uvm.edu/~gmirchan/classes/EE270/EE275/Handouts_Ed4/Ch12%284e%29_Handouts/Ch12%284%29Handouts_4e.pdf