## Copyright (C) 2007 Tiago Charters de Azevedo
##
## 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

function inttrap(a,b,n)
%Trapezoidal integration rule
% Integrates a function f:[a,b]->R  with  n subintervals
format short g;

 if (nargin != 3)
    disp("")
    usage ("Integrates f:[a,b], n sub-intervals");
    disp("")
  endif

disp("")
h=(b-a)/n;
x=[a:h:b];

I=h/2.*(2*sum(f(x))-f(a)-f(b));
endfunction