GNU Octave  3.8.0
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colloc.cc
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1 /*
2 
3 Copyright (C) 1996-2013 John W. Eaton
4 
5 This file is part of Octave.
6 
7 Octave is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by the
9 Free Software Foundation; either version 3 of the License, or (at your
10 option) any later version.
11 
12 Octave is distributed in the hope that it will be useful, but WITHOUT
13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
16 
17 You should have received a copy of the GNU General Public License
18 along with Octave; see the file COPYING. If not, see
19 <http://www.gnu.org/licenses/>.
20 
21 */
22 
23 #ifdef HAVE_CONFIG_H
24 #include <config.h>
25 #endif
26 
27 #include <string>
28 
29 #include "CollocWt.h"
30 #include "lo-mappers.h"
31 
32 #include "defun.h"
33 #include "error.h"
34 #include "oct-obj.h"
35 #include "utils.h"
36 
37 DEFUN (colloc, args, ,
38  "-*- texinfo -*-\n\
39 @deftypefn {Built-in Function} {[@var{r}, @var{amat}, @var{bmat}, @var{q}] =} colloc (@var{n}, \"left\", \"right\")\n\
40 Compute derivative and integral weight matrices for orthogonal\n\
41 collocation using the subroutines given in J. Villadsen and\n\
42 M. L. Michelsen, @cite{Solution of Differential Equation Models by\n\
43 Polynomial Approximation}.\n\
44 @end deftypefn")
45 {
46  octave_value_list retval;
47 
48  int nargin = args.length ();
49 
50  if (nargin < 1 || nargin > 3)
51  {
52  print_usage ();
53  return retval;
54  }
55 
56  if (! args(0).is_scalar_type ())
57  {
58  error ("colloc: N must be a scalar");
59  return retval;
60  }
61 
62  double tmp = args(0).double_value ();
63 
64  if (error_state)
65  return retval;
66 
67  if (xisnan (tmp))
68  {
69  error ("colloc: N cannot be NaN");
70  return retval;
71  }
72 
73  octave_idx_type ncol = NINTbig (tmp);
74  if (ncol < 0)
75  {
76  error ("colloc: N must be positive");
77  return retval;
78  }
79 
80  octave_idx_type ntot = ncol;
82  octave_idx_type right = 0;
83 
84  for (int i = 1; i < nargin; i++)
85  {
86  if (args(i).is_defined ())
87  {
88  if (! args(i).is_string ())
89  {
90  error ("colloc: expecting string argument \"left\" or \"right\"");
91  return retval;
92  }
93 
94  std::string s = args(i).string_value ();
95 
96  if ((s.length () == 1 && (s[0] == 'R' || s[0] == 'r'))
97  || s == "right")
98  {
99  right = 1;
100  }
101  else if ((s.length () == 1 && (s[0] == 'L' || s[0] == 'l'))
102  || s == "left")
103  {
104  left = 1;
105  }
106  else
107  {
108  error ("colloc: unrecognized argument");
109  return retval;
110  }
111  }
112  else
113  {
114  error ("colloc: unexpected empty argument");
115  return retval;
116  }
117  }
118 
119  ntot += left + right;
120  if (ntot < 1)
121  {
122  error ("colloc: the total number of roots must be positive");
123  return retval;
124  }
125 
126  CollocWt wts (ncol, left, right);
127 
128  ColumnVector r = wts.roots ();
129  Matrix A = wts.first ();
130  Matrix B = wts.second ();
131  ColumnVector q = wts.quad_weights ();
132 
133  retval(3) = q;
134  retval(2) = B;
135  retval(1) = A;
136  retval(0) = r;
137 
138  return retval;
139 }