If you know where the missing element(s) belong(s), put NaN(s) there, which will give you a disjointed line:
Year = [2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010];
X = [1 2 1 4 5 6 7 2 3 5 6];
% this:
Y = [1 2 NaN 3 4 5 2 3 1 2 3];
% or this:
Y = [1 2 3 4 5 2 3 1 2 3];
Y = [Y([1 2]) NaN Y(3:end)];
plot(Year,[X;Y])
legend('X','Y')
