n = 3;
a = -1;
b = 1;
function W = calculate_W(x,k)
cheb3 = @(arg) 4*(arg^3)-3*arg;
if(!k>=2)
 disp("k problem")
else
  W = (x^k - (2^(1-k)) * cheb3(x));
end
endfunction

points = [-1,-0.5,0,0.5,1]
points_result = points.^n
points_poly_results = [];
for i=1:size(points,2)
  points_poly_results = [points_poly_results,calculate_W(points(i),n)];
end
points_poly_results

error = max(abs(points_result.-points_poly_results))