'Special grid' on a plot

Hi, I have to draw a 'special grid' on a plot of a signal. Specifically, I need one vertical line after 8s and one 10s after the first (and then periodically in this order: 8s,10s,8s,10s etc etc..) How can I do this? I tried to use meshgrid but without results.

Thank you!

[dpb]

Note the location in a time vector of some number of seconds will be

ix=round(T/dt);

where T is the set of desired times and dt the sample rate...

Answer 1

[Riccardo Brambilla]

Thank you both for your time; I solve the problem in this way!

t = [0:1:size(sx)-1]'./fs;

a = ceil(t(end));
x = [8:18:a];
y = [18:18:a];
z = [x;y];
z = z(:).';

plot(t,sx,t,dx);
legend('pupil sx', 'pupil dx');

ax = gca;
ax.XGrid = 'on';
ax.YGrid = 'off';
ax.XTickMode = 'manual'; % keep the same number of 'grid lines' even after resize
ax.XTick = z;
ax.XMinorTick = 'on';