function S=simpson1(x,y)
  n=length(x)
  h=x(2)-x(1)
  s=y(1)+y(n)
 for i=2:2:n-1
   s=s+4*y(i)
 endfor
 for i=3:2:n-2
   s=s+2*y(i)
 endfor
 S=h/3*s
endfunction