--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main/specfun/inst/zeta.m	Mon Sep 18 18:04:30 2006 +0000
@@ -0,0 +1,35 @@
+# Copyright (C) 2006   Sissou   <sylvain.pelissier@gmail.com>
+##
+## This program 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 of the License, or
+## (at your option) any later version.
+##
+## This program 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 this program; if not, write to the Free Software
+## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+## ZETA compute the Riemann's Zeta function.
+
+
+function z = zeta(t)
+	if (nargin != 1)
+			usage ("zeta(x)");
+	endif
+
+	if(t > 1 && imag(t) == 0)
+		F= @(x) 1./(gamma(t)).*x.^(t-1)./(exp(x)-1);
+		z = quad(F,0,Inf);
+	else
+		if(t<0 && imag(t) == 0)
+			z = 2.^t.*pi.^(t-1).*sin(pi.*t./2).*gamma(1-t).*zeta(1-t);
+		else 
+			error("unable to handle complex arguments");
+		endif
+	endif
+endfunction
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