--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/corefcn/gammainc.cc	Fri Jul 27 15:35:00 2012 -0700
@@ -0,0 +1,230 @@
+/*
+
+Copyright (C) 1997-2012 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/>.
+
+*/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "lo-specfun.h"
+
+#include "defun.h"
+#include "error.h"
+#include "gripes.h"
+#include "oct-obj.h"
+#include "utils.h"
+
+DEFUN (gammainc, args, ,
+  "-*- texinfo -*-\n\
+@deftypefn  {Mapping Function} {} gammainc (@var{x}, @var{a})\n\
+@deftypefnx {Mapping Function} {} gammainc (@var{x}, @var{a}, \"lower\")\n\
+@deftypefnx {Mapping Function} {} gammainc (@var{x}, @var{a}, \"upper\")\n\
+Compute the normalized incomplete gamma function,\n\
+@tex\n\
+$$\n\
+ \\gamma (x, a) = {1 \\over {\\Gamma (a)}}\\displaystyle{\\int_0^x t^{a-1} e^{-t} dt}\n\
+$$\n\
+@end tex\n\
+@ifnottex\n\
+\n\
+@example\n\
+@group\n\
+                                x\n\
+                       1       /\n\
+gammainc (x, a) = ---------    | exp (-t) t^(a-1) dt\n\
+                  gamma (a)    /\n\
+                            t=0\n\
+@end group\n\
+@end example\n\
+\n\
+@end ifnottex\n\
+with the limiting value of 1 as @var{x} approaches infinity.\n\
+The standard notation is @math{P(a,x)}, e.g., Abramowitz and Stegun (6.5.1).\n\
+\n\
+If @var{a} is scalar, then @code{gammainc (@var{x}, @var{a})} is returned\n\
+for each element of @var{x} and vice versa.\n\
+\n\
+If neither @var{x} nor @var{a} is scalar, the sizes of @var{x} and\n\
+@var{a} must agree, and @code{gammainc} is applied element-by-element.\n\
+\n\
+By default the incomplete gamma function integrated from 0 to @var{x} is\n\
+computed.  If \"upper\" is given then the complementary function integrated\n\
+from @var{x} to infinity is calculated.  It should be noted that\n\
+\n\
+@example\n\
+gammainc (@var{x}, @var{a}) @equiv{} 1 - gammainc (@var{x}, @var{a}, \"upper\")\n\
+@end example\n\
+@seealso{gamma, lgamma}\n\
+@end deftypefn")
+{
+  octave_value retval;
+  bool lower = true;
+
+  int nargin = args.length ();
+
+  if (nargin == 3)
+    {
+      if (args(2).is_string ())
+        {
+          std::string s = args(2).string_value ();
+          std::transform (s.begin (), s.end (), s.begin (), tolower);
+          if (s == "upper")
+            lower = false;
+          else if (s != "lower")
+            error ("gammainc: third argument must be \"lower\" or \"upper\"");
+        }
+      else
+        error ("gammainc: third argument must be \"lower\" or \"upper\"");
+
+    }
+
+  if (!error_state && nargin >= 2  && nargin <= 3)
+    {
+      octave_value x_arg = args(0);
+      octave_value a_arg = args(1);
+
+      // FIXME Can we make a template version of the duplicated code below
+      if (x_arg.is_single_type () || a_arg.is_single_type ())
+        {
+          if (x_arg.is_scalar_type ())
+            {
+              float x = x_arg.float_value ();
+
+              if (! error_state)
+                {
+                  if (a_arg.is_scalar_type ())
+                    {
+                      float a = a_arg.float_value ();
+
+                      if (! error_state)
+                        retval = lower ? gammainc (x, a)
+                          : static_cast<float>(1) - gammainc (x, a);
+                    }
+                  else
+                    {
+                      FloatNDArray a = a_arg.float_array_value ();
+
+                      if (! error_state)
+                        retval = lower ? gammainc (x, a)
+                          : static_cast<float>(1) - gammainc (x, a);
+                    }
+                }
+            }
+          else
+            {
+              FloatNDArray x = x_arg.float_array_value ();
+
+              if (! error_state)
+                {
+                  if (a_arg.is_scalar_type ())
+                    {
+                      float a = a_arg.float_value ();
+
+                      if (! error_state)
+                        retval = lower ? gammainc (x, a)
+                          : static_cast<float>(1) - gammainc (x, a);
+                    }
+                  else
+                    {
+                      FloatNDArray a = a_arg.float_array_value ();
+
+                      if (! error_state)
+                        retval = lower ? gammainc (x, a)
+                          : static_cast<float>(1) - gammainc (x, a);
+                    }
+                }
+            }
+        }
+      else
+        {
+          if (x_arg.is_scalar_type ())
+            {
+              double x = x_arg.double_value ();
+
+              if (! error_state)
+                {
+                  if (a_arg.is_scalar_type ())
+                    {
+                      double a = a_arg.double_value ();
+
+                      if (! error_state)
+                        retval = lower ? gammainc (x, a) : 1. - gammainc (x, a);
+                    }
+                  else
+                    {
+                      NDArray a = a_arg.array_value ();
+
+                      if (! error_state)
+                        retval = lower ? gammainc (x, a) : 1. - gammainc (x, a);
+                    }
+                }
+            }
+          else
+            {
+              NDArray x = x_arg.array_value ();
+
+              if (! error_state)
+                {
+                  if (a_arg.is_scalar_type ())
+                    {
+                      double a = a_arg.double_value ();
+
+                      if (! error_state)
+                        retval = lower ? gammainc (x, a) : 1. - gammainc (x, a);
+                    }
+                  else
+                    {
+                      NDArray a = a_arg.array_value ();
+
+                      if (! error_state)
+                        retval = lower ? gammainc (x, a) : 1. - gammainc (x, a);
+                    }
+                }
+            }
+        }
+    }
+  else
+    print_usage ();
+
+  return retval;
+}
+
+/*
+%!test
+%! a = [.5 .5 .5 .5 .5];
+%! x = [0 1 2 3 4];
+%! v1 = sqrt (pi)*erf (x)./gamma (a);
+%! v3 = gammainc (x.*x, a);
+%! assert (v1, v3, sqrt (eps));
+
+%!assert (gammainc (0:4,0.5, "upper"), 1-gammainc (0:4,0.5), 1e-10)
+
+%!test
+%! a = single ([.5 .5 .5 .5 .5]);
+%! x = single ([0 1 2 3 4]);
+%! v1 = sqrt (pi ("single"))*erf (x)./gamma (a);
+%! v3 = gammainc (x.*x, a);
+%! assert (v1, v3, sqrt (eps ("single")));
+
+%!assert (gammainc (single (0:4), single (0.5), "upper"), 
+%!        single (1)-gammainc (single (0:4), single (0.5)),
+%!        single (1e-7))
+*/