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1 /* |
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2 |
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3 Copyright (C) 1997 John W. Eaton |
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4 |
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5 This file is part of Octave. |
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6 |
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7 Octave is free software; you can redistribute it and/or modify it |
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8 under the terms of the GNU General Public License as published by the |
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9 Free Software Foundation; either version 3 of the License, or (at your |
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10 option) any later version. |
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11 |
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12 Octave is distributed in the hope that it will be useful, but WITHOUT |
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13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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15 for more details. |
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16 |
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17 You should have received a copy of the GNU General Public License |
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18 along with Octave; see the file COPYING. If not, see |
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19 <http://www.gnu.org/licenses/>. |
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20 |
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21 */ |
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22 |
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23 #ifdef HAVE_CONFIG_H |
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24 #include <config.h> |
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25 #endif |
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26 |
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27 #include "lo-specfun.h" |
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28 |
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29 #include "defun-dld.h" |
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30 #include "error.h" |
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31 #include "gripes.h" |
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32 #include "oct-obj.h" |
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33 #include "utils.h" |
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34 |
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35 DEFUN_DLD (gammainc, args, , |
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36 "-*- texinfo -*-\n\ |
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37 @deftypefn {Mapping Function} {} gammainc (@var{x}, @var{a})\n\ |
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38 Compute the normalized incomplete gamma function,\n\ |
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39 @iftex\n\ |
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40 @tex\n\ |
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41 $$\n\ |
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42 \\gamma (x, a) = {\\displaystyle\\int_0^x e^{-t} t^{a-1} dt \\over \\Gamma (a)}\n\ |
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43 $$\n\ |
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44 @end tex\n\ |
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45 @end iftex\n\ |
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46 @ifinfo\n\ |
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47 \n\ |
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48 @smallexample\n\ |
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49 x\n\ |
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50 1 /\n\ |
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51 gammainc (x, a) = --------- | exp (-t) t^(a-1) dt\n\ |
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52 gamma (a) /\n\ |
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53 t=0\n\ |
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54 @end smallexample\n\ |
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55 \n\ |
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56 @end ifinfo\n\ |
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57 with the limiting value of 1 as @var{x} approaches infinity.\n\ |
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58 The standard notation is @math{P(a,x)}, e.g. Abramowitz and Stegun (6.5.1).\n\ |
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59 \n\ |
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60 If @var{a} is scalar, then @code{gammainc (@var{x}, @var{a})} is returned\n\ |
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61 for each element of @var{x} and vice versa.\n\ |
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62 \n\ |
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63 If neither @var{x} nor @var{a} is scalar, the sizes of @var{x} and\n\ |
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64 @var{a} must agree, and @var{gammainc} is applied element-by-element.\n\ |
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65 @seealso{gamma, lgamma}\n\ |
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66 @end deftypefn") |
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67 { |
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68 octave_value retval; |
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69 |
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70 int nargin = args.length (); |
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71 |
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72 if (nargin == 2) |
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73 { |
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74 octave_value x_arg = args(0); |
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75 octave_value a_arg = args(1); |
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76 |
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77 if (x_arg.is_scalar_type ()) |
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78 { |
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79 double x = x_arg.double_value (); |
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80 |
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81 if (! error_state) |
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82 { |
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83 if (a_arg.is_scalar_type ()) |
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84 { |
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85 double a = a_arg.double_value (); |
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86 |
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87 if (! error_state) |
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88 retval = gammainc (x, a); |
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89 } |
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90 else |
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91 { |
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92 NDArray a = a_arg.array_value (); |
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93 |
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94 if (! error_state) |
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95 retval = gammainc (x, a); |
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96 } |
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97 } |
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98 } |
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99 else |
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100 { |
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101 NDArray x = x_arg.array_value (); |
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102 |
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103 if (! error_state) |
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104 { |
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105 if (a_arg.is_scalar_type ()) |
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106 { |
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107 double a = a_arg.double_value (); |
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108 |
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109 if (! error_state) |
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110 retval = gammainc (x, a); |
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111 } |
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112 else |
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113 { |
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114 NDArray a = a_arg.array_value (); |
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115 |
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116 if (! error_state) |
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117 retval = gammainc (x, a); |
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118 } |
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119 } |
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120 } |
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121 } |
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122 else |
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123 print_usage (); |
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124 |
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125 return retval; |
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126 } |
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127 |
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128 /* |
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129 ;;; Local Variables: *** |
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130 ;;; mode: C++ *** |
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131 ;;; End: *** |
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132 */ |
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133 |
