home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
OS/2 Shareware BBS: 10 Tools
/
10-Tools.zip
/
octa21fb.zip
/
octave
/
SCRIPTS.ZIP
/
scripts.fat
/
specfun
/
gammai.m
< prev
next >
Wrap
Text File
|
1999-12-24
|
2KB
|
62 lines
## Copyright (C) 1998 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 2, 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, write to the Free
## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
## 02111-1307, USA.
## -*- texinfo -*-
## @deftypefn {Mapping Function} {} gammai (@var{a}, @var{x})
## Computes the incomplete gamma function,
## @iftex
## @tex
## $$
## \gamma (a, x) = {\displaystyle\int_0^x e^{-t} t^{a-1} dt \over \Gamma (a)}
## $$
## @end tex
## @end iftex
## @ifinfo
##
## @smallexample
## x
## 1 /
## gammai (a, x) = --------- | exp (-t) t^(a-1) dt
## gamma (a) /
## t=0
## @end smallexample
## @end ifinfo
##
## If @var{a} is scalar, then @code{gammai (@var{a}, @var{x})} is returned
## for each element of @var{x} and vice versa.
##
## If neither @var{a} nor @var{x} is scalar, the sizes of @var{a} and
## @var{x} must agree, and @var{gammai} is applied element-by-element.
## @end deftypefn
## See also: gamma, lgamma
## Author: jwe
## Created: 30 Jan 1998
function retval = gammai (a, x)
if (nargin == 2)
retval = gammainc (x, a);
else
usage ("gammai (a, x)");
endif
endfunction