update packages

[CreaPhase.git] / octave_packages / m / polynomial / polyder.m

diff --git a/octave_packages/m/polynomial/polyder.m b/octave_packages/m/polynomial/polyder.m
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+## Copyright (C) 1994-2012 John W. Eaton
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {} polyder (@var{p})
+## @deftypefnx {Function File} {[@var{k}] =} polyder (@var{a}, @var{b})
+## @deftypefnx {Function File} {[@var{q}, @var{d}] =} polyder (@var{b}, @var{a})
+## Return the coefficients of the derivative of the polynomial whose
+## coefficients are given by the vector @var{p}.  If a pair of polynomials
+## is given, return the derivative of the product @math{@var{a}*@var{b}}.
+## If two inputs and two outputs are given, return the derivative of the
+## polynomial quotient @math{@var{b}/@var{a}}.  The quotient numerator is
+## in @var{q} and the denominator in @var{d}.
+## @seealso{polyint, polyval, polyreduce}
+## @end deftypefn
+
+## Author: Tony Richardson <arichard@stark.cc.oh.us>
+## Created: June 1994
+## Adapted-By: jwe
+
+function [q, d] = polyder (p, a)
+
+  if (nargin == 1 || nargin == 2)
+    if (! isvector (p))
+      error ("polyder: argument must be a vector");
+    endif
+    if (nargin == 2)
+      if (! isvector (a))
+        error ("polyder: argument must be a vector");
+      endif
+      if (nargout == 1)
+        ## derivative of p*a returns a single polynomial
+        q = polyder (conv (p, a));
+      else
+        ## derivative of p/a returns numerator and denominator
+        d = conv (a, a);
+        if (numel (p) == 1)
+          q = -p * polyder (a);
+        elseif (numel (a) == 1)
+          q = a * polyder (p);
+        else
+          q = conv (polyder (p), a) - conv (p, polyder (a));
+          q = polyreduce (q);
+        endif
+
+        ## remove common factors from numerator and denominator
+        x = polygcd (q, d);
+        if (length(x) != 1)
+          q = deconv (q, x);
+          d = deconv (d, x);
+        endif
+
+        ## move all the gain into the numerator
+        q = q/d(1);
+        d = d/d(1);
+      endif
+    else
+      lp = numel (p);
+      if (lp == 1)
+        q = 0;
+        return;
+      elseif (lp == 0)
+        q = [];
+        return;
+      endif
+
+      ## Force P to be a row vector.
+      p = p(:).';
+
+      q = p(1:(lp-1)) .* [(lp-1):-1:1];
+    endif
+  else
+    print_usage ();
+  endif
+
+endfunction
+
+
+%!assert(all (all (polyder ([1, 2, 3]) == [2, 2])));
+%!assert(polyder (13) == 0);
+
+%!error polyder ([]);
+%!error polyder ([1, 2; 3, 4]);
+