%   A sample code for quiz 03, problem 05 
%   to evaluate Lagrange interpolating polynomials
%   and interpolation directly.

clear all
format long

x = 0.3:.1:.6 
y = exp(-2*x) 
z = x-y;
n = 3;
zz = 0;
       
for k = 1:n+1
  L(k) = 1.;
 for i = 1:n+1
    if ( i ~= k ) 
      L(k) =  L(k)*(zz-z(i))/(z(k)-z(i));
    end
  end
end

xx = 0.;
for k = 1:n+1
  xx = xx + x(k)*L(k);
end
xx