[Octave-cvsupdate] SF.net SVN: octave:[10907] trunk/octave-forge/main/control/inst/arx.m

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

Revision: 10907
          http://octave.svn.sourceforge.net/octave/?rev=10907&view=rev
Author:   paramaniac
Date:     2012-08-24 15:45:12 +0000 (Fri, 24 Aug 2012)
Log Message:
-----------
control: improve doc and argument checking

Modified Paths:
--------------
    trunk/octave-forge/main/control/inst/arx.m

Modified: trunk/octave-forge/main/control/inst/arx.m
===================================================================
--- trunk/octave-forge/main/control/inst/arx.m	2012-08-24 09:33:05 UTC (rev 10906)
+++ trunk/octave-forge/main/control/inst/arx.m	2012-08-24 15:45:12 UTC (rev 10907)
@@ -22,6 +22,19 @@
 ## @deftypefnx {Function File} {[@var{sys}, @var{x0}] =} arx (@var{dat}, @var{'na'}, @var{na}, @var{'nb'}, @var{nb})
 ## Estimate ARX model using QR factorization.
 ##
+## @iftex
+## @tex
+## $$ A(q) \\, y(t) = B(q) \\, u(t) \\, + \\, e(t) $$
+## @end tex
+## @end iftex
+## @ifnottex
+##
+## @example
+## A(q) y(t) = B(q) u(t) + e(t)
+## @end example
+##
+## @end ifnottex
+##
 ## @strong{Inputs}
 ## @table @var
 ## @item dat
@@ -58,6 +71,12 @@
 ## @item 'nb'
 ## Order of the polynomial B(q)+1 and number of zeros+1.
 ## @var{nb} <= @var{na}.
+##
+## @item 'nk'
+## Input-output delay specified as number of sampling instants.
+## Scalar positive integer.  This corresponds to a call to command
+## @command{nkshift}, followed by padding the B polynomial with
+## @var{nk} leading zeros.
 ## @end table
 ##
 ##
@@ -118,16 +137,14 @@
     key = lower (varargin{k});
     val = varargin{k+1};
     switch (key)
-      ## TODO: proper argument checking
       case "na"
-        na = val;
+        na = __check_n__ (val, "na");
       case "nb"
-        nb = val;
+        nb = __check_n__ (val, "nb");
       case "nk"
-        if (issample (val, 0) && fix (val) == val)  # individual, channel-wise nk not supported yet
-          nk = val;
-        else
-          error ("arx: argument 'nk' must be a positive integer");
+        nk = __check_n__ (val, "nk");
+        if (! issample (val, 0))
+          error ("arx: channel-wise 'nk' matrices not supported yet");
         endif
       otherwise
         warning ("arx: invalid property name '%s' ignored", key);
@@ -281,3 +298,12 @@
   x = V * (S .\ (U' * b));                          # U' is the conjugate transpose
 
 endfunction
+
+
+function val = __check_n__ (val, str = "n")
+  
+  if (! is_real_matrix (val) || fix (val) != val)
+    error ("arx: argument '%s' must be a positive integer", str);
+  endif
+
+endfunction

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