ax.XTick will only set the ticks values along the x-axis. What is the actual range of x?
As far as I can assume the values of x:
x=[1:8];
y1=[12 13 15 16];
...
...
...
... and so on
plot(x(1),y1, "--o", x(2), y2,"--o", x(3), y3,"--o", x(4), y4,"--o"); % similarly for x(5), y5 to x(6) to y6
xticks([ 1 2 3 4 5 6 7 8 ])
Xticklabels({'07:00AM','08:00AM','9:00AM','10:00AM','11:00AM','12:00PM','1:00PM','2:00PM'});
The code can be improved if you use loops and combine all the y values in a single matrix (cell arrays).
