PROGRAM INTEGRAL dengan GAUSSIAN_LEGENDRE QUADRATURE

%GausQuad - integral dengan Gaussian-Legendre Quadrature
% dengan orde n = 5.
clear; help GausQuad;
a=input('Batas bawah integral - ');
b=input('Batas atas integral - ');
% akar Pn(x)
x1=0.9061798459;
x2=0.5384693101;
x3=0.000;
x4= -x1;
x5= -x2;
% koefisien
c1=0.2369268851;
c2=0.4786286705;
c3=0.5688888889;
c4=c1;
c5=c2;
% transformasi variabel
dz=(b-a)/2;
dx=(b+a)/2;
% ganti fungsi bila perlu
[f1 par]=errf(dz*x1+dx);
[f2 par]=errf(dz*x2+dx);
[f3 par]=errf(dz*x3+dx);
[f4 par]=errf(dz*x4+dx);
[f5 par]=errf(dz*x5+dx);
% hasil integral
I = par*(c1*f1 + c2*f2 + c3*f3 + c4*f4 + c5*f5)*dz;
fprintf('Hasil integral = %g\n', I);