How can I create a datetick using if statements?

I am trying to create datetick variables to be plotted in the x-axis of a curve.

The code I am trying to create must start with the time of 7:00 am wich I am going to asign the variable TODAY. The magnitude of TODAY must extend from 7:00 am to 12:00 pm, and then switch to another variable, REST_OF_TODAY that extends from 12:00 pm to 5:00 pm.

Basically what I was thinking of is somekind of if statement that when the datetick function reaches the 12:00 pm value switch the variable name from TODAY to REST_OF_TODAY.

 TODAY = 7:00 am - 12:00 pm
 REST_OF_TODAY = 12:00 pm - 5:00 pm

Can you please help?

[Azzi Abdelmalek]

how many plots ?

[jjlivestrong]

One plot only.

Answer 1

[Matt Tearle]

Do you actually want to create a variable that has two states or is this just about how you visualize a time series? If it's the latter, you can easily just adjust the axis properties

x = linspace(7,17);
plot(x,sin(sqrt(x)*pi))
set(gca,'XTick',[7,12],'XTickLabel',{'Today','Rest of today'})

Or, if time is given in terms of date numbers:

t1 = datenum([2012 9 21 7 0 0])   % 7 am today
t2 = datenum([2012 9 21 17 0 0])  % 5 pm
x = linspace(t1,t2);
plot(x,sin(sqrt(x-t0)*pi))
set(gca,'XTick',[t1,floor(t1)+0.5],'XTickLabel',{'Today','Rest of today'})

Answer 2

[Azzi Abdelmalek]

TODAY =  7/24 : 1/(24):12/24;  %or  TODAY=12/24 :1/(24): 17/24
plot(TODAY ,rand(1,6))
set(gca,'xtick',TODAY)
datetick('x','keepticks')