GNU Octave  4.0.0 A high-level interpreted language, primarily intended for numerical computations, mostly compatible with Matlab
rcond.cc
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1 /*
2
3 Copyright (C) 2008-2015 David Bateman
4
5 This file is part of Octave.
6
7 Octave is free software; you can redistribute it and/or modify it
9 Free Software Foundation; either version 3 of the License, or (at your
10 option) any later version.
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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.
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17 You should have received a copy of the GNU General Public License
18 along with Octave; see the file COPYING. If not, see
20
21 */
22
23 #ifdef HAVE_CONFIG_H
24 #include <config.h>
25 #endif
26
27 #include "defun.h"
28 #include "error.h"
29 #include "gripes.h"
30 #include "oct-obj.h"
31 #include "utils.h"
32
33 DEFUN (rcond, args, ,
34  "-*- texinfo -*-\n\
35 @deftypefn {Built-in Function} {@var{c} =} rcond (@var{A})\n\
36 Compute the 1-norm estimate of the reciprocal condition number as returned\n\
37 by @sc{lapack}.\n\
38 \n\
39 If the matrix is well-conditioned then @var{c} will be near 1 and if the\n\
40 matrix is poorly conditioned it will be close to 0.\n\
41 \n\
42 The matrix @var{A} must not be sparse. If the matrix is sparse then\n\
43 @code{condest (@var{A})} or @code{rcond (full (@var{A}))} should be used\n\
45 @seealso{cond, condest}\n\
46 @end deftypefn")
47 {
48  octave_value retval;
49
50  int nargin = args.length ();
51
52  if (nargin != 1)
53  print_usage ();
54  else if (args(0).is_sparse_type ())
55  error ("rcond: for sparse matrices use 'rcond (full (a))' or 'condest (a)' instead");
56  else if (args(0).is_single_type ())
57  {
58  if (args(0).is_complex_type ())
59  {
60  FloatComplexMatrix m = args(0).float_complex_matrix_value ();
61  MatrixType mattyp;
62  retval = m.rcond (mattyp);
63  args(0).matrix_type (mattyp);
64  }
65  else
66  {
67  FloatMatrix m = args(0).float_matrix_value ();
68  MatrixType mattyp;
69  retval = m.rcond (mattyp);
70  args(0).matrix_type (mattyp);
71  }
72  }
73  else if (args(0).is_complex_type ())
74  {
75  ComplexMatrix m = args(0).complex_matrix_value ();
76  MatrixType mattyp;
77  retval = m.rcond (mattyp);
78  args(0).matrix_type (mattyp);
79  }
80  else
81  {
82  Matrix m = args(0).matrix_value ();
83  MatrixType mattyp;
84  retval = m.rcond (mattyp);
85  args(0).matrix_type (mattyp);
86  }
87
88  return retval;
89 }
90
91 /*
92 %!assert (rcond (eye (2)), 1)
93 %!assert (rcond (ones (2)), 0)
94 %!assert (rcond ([1 1; 2 1]), 1/9)
95 %!assert (rcond (magic (4)), 0, eps)
96
97 %!shared x, sx
98 %! x = [-5.25, -2.25; -2.25, 1] * eps () + ones (2) / 2;
99 %! sx = [-5.25, -2.25; -2.25, 1] * eps ("single") + ones (2) / 2;
100 %!assert (rcond (x) < eps ());
101 %!assert (rcond (sx) < eps ('single'));
102 %!assert (rcond (x*i) < eps ());
103 %!assert (rcond (sx*i) < eps ('single'));
104
105 */
OCTINTERP_API void print_usage(void)
Definition: defun.cc:51
#define DEFUN(name, args_name, nargout_name, doc)
Definition: defun.h:44
void error(const char *fmt,...)
Definition: error.cc:476
double rcond(void) const
Definition: dMatrix.cc:1392
double rcond(void) const
Definition: CMatrix.cc:1750
octave_idx_type length(void) const
Definition: ov.cc:1525
Definition: dMatrix.h:35
float rcond(void) const
Definition: fMatrix.cc:1403
float rcond(void) const
Definition: fCMatrix.cc:1754