x = [5,-4,-3,0,2];
xi = -4:0.1:2;
y = [8,-5,16,-2,-1];
i1 = interp1(x,y,xi,'cubic');
i2 = interp1(x,y,xi,'linear');
i3 = interp1(x,y,xi,'spline');
plot(xi,i1,xi,i2,'r-')
hold on
plot(xi,i3,'b-',x,y,'Og')