[Octave-cvsupdate] SF.net SVN: octave:[10372] trunk/octave-forge/main/control/inst

[<par...@us...>]

Revision: 10372
          http://octave.svn.sourceforge.net/octave/?rev=10372&view=rev
Author:   paramaniac
Date:     2012-05-07 04:39:42 +0000 (Mon, 07 May 2012)
Log Message:
-----------
control: handle special case num=0 or den=1 when displaying z^-1

Modified Paths:
--------------
    trunk/octave-forge/main/control/inst/@tf/display.m
    trunk/octave-forge/main/control/inst/filt.m

Modified: trunk/octave-forge/main/control/inst/@tf/display.m
===================================================================
--- trunk/octave-forge/main/control/inst/@tf/display.m	2012-05-07 03:27:54 UTC (rev 10371)
+++ trunk/octave-forge/main/control/inst/@tf/display.m	2012-05-07 04:39:42 UTC (rev 10372)
@@ -66,9 +66,11 @@
   
   tfp = isa (num, "tfpoly");
 
-  if (tfp && num == 0)
+  if (num == tfpoly (0))
     str = [" ", name, ":  0"];
-  elseif (tfp && den == 1)
+  elseif ((tfp && den == 1) || (! tfp && isequal (den, 1)))
+  ## elseif (den == tfpoly (1)) doesn't work because it
+  ## would mistakingly accept non-tfpoly denominators like [0, 1]
     str = [" ", name, ":  "];
     numstr = tfpoly2str (num, tfvar);
     str = [str, numstr];

Modified: trunk/octave-forge/main/control/inst/filt.m
===================================================================
--- trunk/octave-forge/main/control/inst/filt.m	2012-05-07 03:27:54 UTC (rev 10371)
+++ trunk/octave-forge/main/control/inst/filt.m	2012-05-07 04:39:42 UTC (rev 10372)
@@ -78,11 +78,13 @@
   switch (nargin)
     case 0              # filt ()
       sys = tf ();
+      ## sys.inv = true;
       return;
 
     case 1              # filt (sys), filt (matrix)
       if (isa (num, "lti") || is_real_matrix (num))
         sys = tf (num);
+        ## sys.inv = true;  # would be a problem for continuous-time LTI models
         return;
       else
         print_usage ();
@@ -115,7 +117,9 @@
       den = cellfun (@postpad, den, lmax, "uniformoutput", false);
 
       ## use standard tf constructor
-      ## sys is stored and displayed in standard z form, not z^-1
+      ## sys is stored in standard z form, not z^-1
+      ## so we can mix it with regular transfer function models
+      ## property "inv", true displays sys in z^-1 form
       sys = tf (num, den, tsam, "inv", true, varargin{:});
   endswitch
 

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