Matlab - updating objects on a plot - matlab

Question

I am trying to add a timer a simulation i am working on. At the moment i can get the timer to display in the location i want, however i cant make the numbers clear each other, i.e they all just stack on top of each other slowly creating a solid black mess. I have tried implementing a clf function but it just clears the entire figure. The code for the timer is:
HH = 0; MM = 0; SS = 0;
timer = sprintf('%02d:%02d:%02d',HH,MM,SS);
text(-450,450,timer); %% adjust location of clock in graph using the first two arguments: (x,y) coordinates
for t = 1:86400
SS = SS + 1;
if SS == 60
MM = MM + 1;
SS = 0;
end
if MM == 60
HH = HH + 1;
MM = 0;
end
timer = sprintf('%02d:%02d:%02d',HH,MM,SS); %% construct time string after all adjustments to HH, MM, SS
clf(f,'reset'); %% clear previous clock display
text(-450,450,timer); %% re-plot time to figure
if t == EventTimes(1)
uav1 = uav1.uavSetDestin([event1(2:3) 0]);
plot(event1(2),event1(3),'+')
hold on
end
if t == EventTimes(2)
uav2 = uav2.uavSetDestin([event2(2:3) 0]);
plot(event2(2),event2(3),'r+')
hold on
end
Is there a way i can reset only the timer function so it displays properly?

Answer 1

You want to store the handle to the text object and update the String property of this existing object rather than creating a new text object every time.
%// The first time through your loop
htext = text(-450, 450, timer);
%// Every other time through the loop
set(htext, 'String', sprintf('%02d:%02d:%02d',HH,MM,SS)
You will also want to do something similar with the plot objects rather than clearing the figure and redrawing all of the plots every iteration.
Integrating this with your code we get something like:
%// Create the initial text object
HH = 0; MM = 0; SS = 0;
timerString = sprintf('%02d:%02d:%02d',HH,MM,SS);
htext = text(-450, 450, timeString);
%// Create the plot objects
hplot1 = plot(NaN, NaN, '+');
hplot2 = plot(NaN, NaN, 'r+');
for t = 1:86400
SS = SS + 1;
%// I could help myself and made this significantly shorter
MM = MM + (mod(SS, 60) == 0);
HH = HH + (mod(MM, 60) == 0);
%// Update the timer string
timerString = sprintf('%02d:%02d:%02d',HH,MM,SS);
set(htext, 'String', timerString);
%// Update your plots depending upon which EventTimes()
if t == EventTimes(1)
uav1 = uav1.uavSetDestin([event1(2:3) 0]);
set(hplot1, 'XData', event1(2), 'YData', event1(3));
elseif t == EventTimes(2)
uav2 = uav2.uavSetDestin([event2(2:3) 0]);
set(hplot2, 'XData', event2(2), 'YData', event2(3));
end
%// Force a redraw event
drawnow;
end