trapc.m

来自「sareli<matlab科学计算>配套程序」· M 代码 · 共 24 行

function [Itpc]=trapc(a,b,M,f,choice,varargin)
%TRAPC Composite two-points numerical integration.
%   ITPC = TRAPC(A,B,M,FUN,CHOICE) computes an approximation of the integral 
%   of the function FUN via the trapezoidal method (with M equispaced intervals)
%   if CHOICE=1, via the Gauss composite formula if CHOICE=2.
%   FUN accepts real scalar input x and returns a real scalar
%   value. FUN can also be an inline object.
H=(b-a)/M;
switch choice	
case 1,
  x=linspace(a,b,M+1); 
  fpm=feval(f,x,varargin{:}); 
  fpm(2:end-1)=2*fpm(2:end-1); 
  Itpc=0.5*H*sum(fpm);
case 2,
  z=linspace(a,b,M+1); 
  x=z(1:end-1)+H/2*(1-1/sqrt(3)); 
  x=[x, x+H/sqrt(3)]; 
  fpm=feval(f,x,varargin{:}); 
  Itpc=0.5*H*sum(fpm);
otherwise
  disp('Unknown formula');
end
return