x0=[0 3 5 7 9 11 12 13 14 15 ];
y0=[0 1.2 1.7 2.0 2.1 2.0 1.8 1.2 1.0 1.6 ];
x=0:0.1:15;
y1=lagr1(x0,y0,x);
y2=interp1(x0,y0,x);
y3=interp1(x0,y0,x,'spline');
subplot(3,1,1)
plot(x0,y0,'k+',x,y1,'r')
grid
title('lagrange')
subplot(3,1,2)
plot(x0,y0,'k+',x,y2,'r')
grid
title('piecewise linear')
subplot(3,1,3)
plot(x0,y0,'k+',x,y3,'r')
grid
title('spline')