Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / control-2.3.52 / issample.m

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+## Copyright (C) 1996, 2000, 2002, 2003, 2004, 2005, 2007
+##               Auburn University.  All rights reserved.
+##
+## This program 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.
+##
+## This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{bool} =} issample (@var{ts})
+## @deftypefnx {Function File} {@var{bool} =} issample (@var{ts}, @var{flg})
+## Return true if @var{ts} is a valid sampling time.
+##
+## @strong{Inputs}
+## @table @var
+## @item ts
+## Alleged sampling time to be tested.
+## @item flg = 1
+## Accept real scalars @var{ts} > 0.  Default Value.
+## @item flg = 0
+## Accept real scalars @var{ts} >= 0.
+## @item flg = -1
+## Accept real scalars @var{ts} > 0 and @var{ts} == -1.
+## @item flg = -10
+## Accept real scalars @var{ts} >= 0 and @var{ts} == -1.
+## @item flg = -2
+## Accept real scalars @var{ts} >= 0, @var{ts} == -1 and @var{ts} == -2.
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item bool
+## True if conditions are met and false otherwise.
+## @end table
+##
+## @end deftypefn
+
+## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu>
+## Created: July 1995
+
+## Adapted-By: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Date: September 2009
+## Version: 0.3
+
+function bool = issample (tsam, flg = 1)
+
+  if (nargin < 1 || nargin > 2)
+    print_usage (); 
+  endif
+
+  switch (flg)
+    case 1    # discrete
+      bool = is_real_scalar (tsam) && (tsam > 0);
+    case 0    # continuous or discrete
+      bool = is_real_scalar (tsam) && (tsam >= 0);
+    case -1   # discrete, tsam unspecified
+      bool = is_real_scalar (tsam) && (tsam > 0 || tsam == -1);
+    case -10  # continuous or discrete, tsam unspecified
+      bool = is_real_scalar (tsam) && (tsam >= 0 || tsam == -1);
+    case -2   # accept static gains
+      bool = is_real_scalar (tsam) && (tsam >= 0 || tsam == -1 || tsam == -2);
+    otherwise
+      print_usage ();
+  endswitch
+
+endfunction
+
+
+## flg == 1
+%!assert (issample (1))
+%!assert (issample (pi))
+%!assert (issample (0), false)
+%!assert (issample (-1), false)
+%!assert (issample (-1, 1), false)
+%!assert (issample ("a"), false)
+%!assert (issample (eye (2)), false)
+%!assert (issample (2+2i), false)
+
+## flg == 0
+%!assert (issample (1, 0))
+%!assert (issample (0, 0))
+%!assert (issample (-1, 0), false)
+%!assert (issample (pi, 0))
+%!assert (issample ("b", 0), false)
+%!assert (issample (rand (3,2), 0), false)
+%!assert (issample (2+2i, 0), false)
+%!assert (issample (0+2i, 0), false)
+
+## flg == -1
+%!assert (issample (-1, -1))
+%!assert (issample (0, -1), false)
+%!assert (issample (1, -1))
+%!assert (issample (pi, -1))
+%!assert (issample (-pi, -1), false)
+%!assert (issample ("b", -1), false)
+%!assert (issample (rand (3,2), -1), false)
+%!assert (issample (-2+2i, -1), false)
+
+## errors
+%!error (issample (-1, "ab"))
+%!error (issample ())
+%!error (issample (-1, -1, -1))
+%!error (issample (1, pi))
+%!error (issample (5, rand (2,3)))
+%!error (issample (0, 1+2i))