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%    Copyright (c) 2004.  Takayuki Osogami.  All Rights Reserved.   %
%                                                                   %
% Permission to use, copy, modify, and distribute this source code  %
% and its documentation for any purpose, without fee, and without   %
% a written agreement, is hereby granted, provided that the above   %
% copyright notice, this paragraph and the following two paragraphs %
% appear in all copies, modifications, and distributions.           %
% Created by Takayuki Osogami, Department of Computer Science,      %
% Carnegie Mellon University.                                       %
%                                                                   %
% IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR ANY       %
% DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS   %
% SOURCE CODE AND ITS DOCUMENTATION, EVEN IF THE AUTHOR HAS BEEN    %
% ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.                        %
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% THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,      %
% BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY     %
% AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOURCE CODE AND        %
% ACCOMPANYING DOCUMENTATION, IF ANY, PROVIDED HEREUNDER IS         %
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% MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.    %
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%
% Usage: momentofPH(a,T,k)
%
% Given a PH distribution (a,T), 
% the function returns the k-th moment.
%
% author: Takayuki Osogami
%         Department of Computer Science
%         Carnegie Mellon University
%         osogami@cs.cmu.edu
% date: January 6, 2003

function [moment] = momentofPH(a,T,k)

d = size(a);
e = ones(d(2),1);

moment = (-1)^k * factorial(k) * a * (inv(T))^k * e;