[Octave-bug-tracker] [bug #44930] signal/zplane.m shows non-existent poles and zeros

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?44930>

                 Summary: signal/zplane.m shows non-existent poles and zeros
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Sun 26 Apr 2015 14:40:47 UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Robert Jenssen
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.0.0-rc3
        Operating System: GNU/Linux

    _______________________________________________________

Details:

zplane() is a pole/zero plotter from the signal-1.3.1 package. I sometimes
want to plot the zeros of a single polynomial, not a transfer function. For
example, zplane([1 2 3]) plots a pole at the origin implying a factor of
1/(z^(-1)-0). The example of a transfer function, H(z), is incorrect. The two
transfer functions shown on the right of the "="s are not equal. They differ
by a power of z^(-1).

Also the "N-M" or "M-N" triggers the "Octave:neg-dim-as-zero" warning.

Here is a diff showing my proposed change to the Octave code in
signal/zplane.m:



$diff -U 3 /usr/local/share/octave/packages/signal-1.3.1/zplane.m zplane.m

--- /usr/local/share/octave/packages/signal-1.3.1/zplane.m      2015-04-25
13:43:13.250880797 +1000
+++ zplane.m    2015-04-27 00:13:59.679500075 +1000
@@ -70,10 +70,8 @@
       if isempty(z), z=1; endif
       if isempty(p), p=1; endif
 
-      M = length(z) - 1;
-      N = length(p) - 1;
-      z = [ roots(z); zeros(N - M, 1) ];
-      p = [ roots(p); zeros(M - N, 1) ];
+      z=roots(z);
+      p=roots(p);
     endif
   endif






    _______________________________________________________

Reply to this item at:

  <http://savannah.gnu.org/bugs/?44930>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.gnu.org/