function val=test_interp(a, b, H, h, f)
x=a:H:b;
y=f(x);
xi=a:h:b;
[yi, c]=myinterp(x,y,xi);
plot(xi, yi, 'blue');
hold on
plot(xi,f(xi), 'red');
x=a:H*0.5:b;
y=f(x);
[yi, c]=myinterp(x,y,xi);
plot(xi,yi, 'green');
hold off
