Normalize axis scale for annotations

I want to label a simple plot for some notes:

hf = figure;
x = -180:180; 
f = @(x) 0.09*sech(-x/18);
plot(x, f(x));
ha = annotation('arrow');
ha.Parent = hf.CurrentAxes;  % associate annotation with current axes
% now you can use data units
ha.Y = [50 20];
ha.X = [f(20) f(20)];

annotation("doublearrow", [0.45 0.45], [0.1 1]); 

The trouble is, I want to use the coordinates from the plot, not the "normalized" figure coordinates. How can I rescale them so that

annotation("doublearrow", [0.45 0.45], [0.1 1]); 

becomes

annotation("doublearrow", [0 0], [0 1]); 

Thanks

[Dyuman Joshi]

You can use rescale on the values and then provide them as input to annotation().

Answer 1

[Austin M. Weber]

The text function allows you to place annotations on a figure using axes coordinates. For example:

hf = figure;
x = -180:180; 
f = @(x) 0.09*sech(-x/18);
plot(x, f(x));
ha = annotation('arrow');
ha.Parent = hf.CurrentAxes;  % associate annotation with current axes
% now you can use data units
ha.Y = [50 20];
ha.X = [f(20) f(20)];
% Add annotations
hold on
    text(0,0.08,'⇑','FontSize',20,...
        'HorizontalAlignment','center') % Other double arrows: ⇐ ⇑ ⇒ ⇓ 
hold off

I'm sure there is a way that you can use the annotation function to do what you want, but I think this method might be easier. I would have to play around with annotation to see how it might work.