# Normalize axis scale for annotations

8 views (last 30 days)
HC98 on 28 Feb 2024
Commented: Dyuman Joshi on 29 Feb 2024
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 on 29 Feb 2024
You can use rescale on the values and then provide them as input to annotation().

Austin M. Weber on 28 Feb 2024
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)];
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.

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