do_lagranp.m

辛普森方法

x = -5.0:1:5.0;
y = feval(@f,x); % given data points
%Newton = newtonp(x,y); % find the Newton polynomial
%l = lagranp(x,y); % find the Lagrange polynomial
xx = [-5: 0.05 : 5]; 
%yy = polyval(l,xx); %interpolate for [-5,5]
%yy = polyval(Newton,xx); %interpolate for [-5,5]
%yy = piecelin(x,y,xx); 
yy = pchiptx(x,y,xx);
clf, plot(xx,yy) %plot the graph