Refresh annotate on figure in loop

Hello.

I have read several other solutions that use various methods to replace an annotation with each figure refresh, but none of them seem to work for me. The annotations just keep stacking to the side of the first.

I've tried the solutions found here (to no avail):

https://www.mathworks.com/matlabcentral/answers/334288-how-do-i-delete-all-annotations-on-a-figure-but-not-do-clf

https://www.mathworks.com/matlabcentral/answers/423459-how-to-refresh-annotation-after-each-frame

https://www.mathworks.com/matlabcentral/answers/398319-anottations-are-overlapping-in-each-loop-interaction

figure;
a1 = [];
a2 = [];
for k = 1:K
    %compute indices for the current frame
    n = (1:N)+(N*(k-1));
    
    %signal 1
    x = s1(n);
    E_m1(k) = (x'*x)/N; %Normalized frame energy
    
    subplot(211);
    plot(n,s1(n),'b',n,e(n),'g:');
    
    %annotation stuff
    str1 = sprintf('NFE %d', E_m1);
    dim1 = [0.662 0.622 .3 .3];
    delete(a1);
    a1 = annotation('textbox',dim1,'string',str1,'FitBoxToText','on');
    
    %pause between frames, waiting for keypress
    pause(1)
    
end

Thanks for your time.

Answer 1

[Rik]

Create the annotation object once, and update the String property inside your loop.

I would suggest drawnow to trigger the update of the graphics and to process any queued callbacks (e.g. those triggered by keypresses).

[Tharon]

I don't think this is what I'm trying to do. I need two annotations (a1, a2) because I am concurrently annotating two subplots with different annotations. The second subplot is in the same loop. Both annotations receive the updated values to the right of the original annotation instead of in replacement of. The code above is just an example of what one of the subplots annotation attempt looks like.

The solution found here: https://www.mathworks.com/matlabcentral/answers/398319-anottations-are-overlapping-in-each-loop-interaction

Is exactly what I want to do, but it does not work for me. Could it be because my x-axis values change with each loop iteration?

[Rik]

I don't see the problem of having two annotations, you just have to keep track of two handles:

figure;
a1 = [];
a2 = [];
for k = 1:K
    %compute indices for the current frame
    n = (1:N)+(N*(k-1));
    
    %signal 1
    x = s1(n);
    E_m1(k) = (x'*x)/N; %Normalized frame energy
    
    %signal 2
    x = s2(n);
    E_m2(k) = (x'*x)/N; %Normalized frame energy
    
    ax1=subplot(2,1,1);
    plot(n,s1(n),'b',n,e(n),'g:','Parent',ax1);
    %                            ^^^^^^^^^^^^
    %            use explicit handles here as well
    
    %annotation stuff
    str1 = sprintf('NFE %d', E_m1);
    str2 = sprintf('NFE %d', E_m2);
    dim1 = [0.662 0.622 .3 .3];
    dim2 = ___;
    if k==1
        a1 = annotation('textbox',dim1,'string',str1,'FitBoxToText','on');
        a2 = annotation('textbox',dim2,'string',str2,'FitBoxToText','on');
    else
        set(a1,'Position',dim1,'String',str1);
        set(a2,'Position',dim2,'String',str2);
        drawnow;%trigger graphics update
    end
    
    %pause between frames, waiting for keypress
    pause(1)
end

[Tharon]

Thank you, I will try this soon.

[Tharon]

Thanks for all of your help so far Rik, but I am still having trouble. I implemented the changes you suggested. Now it seems that instead of stacking the new annotations to the right, it stacks them under the previous: