%do_lagranp.m
x = [-2 -1 1 2]; y = [-6 0 0 6]; % given data points
l = lagranp(x,y) % find the Lagrange polynomial
xx = [-2: 0.02 : 2]; yy = polyval(l,xx); %interpolate for [-2,2]
clf, plot(xx,yy,'b', x,y,'*') %plot the graph