gamma.m

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% GAMMA   僈儞儅娭悢
% 
% 丂Y = GAMMA(X) 偼丄X 偺奺梫慺偵懳偡傞僈儞儅娭悢偱偡丅
% 丂X 偼丄幚悢偱側偗傟偽側傝傑偣傫丅
% 丂僈儞儅娭悢偼偮偓偺傛偆偵掕媊偝傟傑偡丅
%
%  丂gamma(x) = t^(x-1) exp(-t) dt 偺0偐傜inf傑偱偺愊暘
%
% 丂僈儞儅娭悢偼丄奒忔娭悢傪撪憓偟傑偡丅
% 丂惍悢 n 偵懳偟偰丄gamma(n+1) = n! (n 偺奒忔) = prod(1:n)偲側傝傑偡丅
%
% 嶲峫  GAMMALN, GAMMAINC, PSI.


%   C. B. Moler, 5-7-91, 11-4-92.
%   Ref: Abramowitz & Stegun, Handbook of Mathematical Functions, sec. 6.1.
%   Copyright 1984-2004 The MathWorks, Inc.