Updating textbox with variable

So i have plot that i want to connect a textbox to, so the textbox counts how many steps the person has done. The plot is a live, updating plot and i need the textbox to do the same. The format im after is "Steps: (no. steps)" which will be adding one each time. Here is the code im currently using although it doesnt work.

while (toc<30) %Loop when Plot is Active will run until plot is closed

vx=readVoltage(a,'A0');

vy=readVoltage(a,'A1');

.........

steps = stepleftacc + steprightacc

set(plotGraph,'XData',time,'YData',data);

axis([0 time(count) -90 90]);

pause(delay);

annotation('textbox',[0.75, 0.1, 0.1, 0.1],'string', "steps:" + steps)

This gives a textbox however the changing variable 'steps' seems to rewrite over itself, any solutions ot fix this?

Thanks

Answer 1

[Geoff Hayes]

George - if you want to just update the existing annotation (rather than creating a new one on each iteration of the while loop) then you need to store the handle to the annotation and then use it for the update. For example,

hAnnotation = annotation('textbox',[0.75, 0.1, 0.1, 0.1],'string', "");
hold on;
while (toc<30) %Loop when Plot is Active will run until plot is closed
    vx=readVoltage(a,'A0');
    vy=readVoltage(a,'A1');
    %.........
    steps = stepleftacc + steprightacc
    set(plotGraph,'XData',time,'YData',data);
    axis([0 time(count) -90 90]);
    pause(delay);
    set(hAnnotation, 'String', "steps:" + steps);
    % etc.
end

We create the annotaiton object outside of the loop and then update it on each iteration.