text box for 'xline' function?

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Hello, (probably this is an easy question) using the function ‘xline’ in order to represent a statistical value, how can I add a text box with its respective value pointing with an arrow the middle of the line? Thanks.

Accepted Answer

Scott MacKenzie
Scott MacKenzie on 2 Jun 2021
Edited: Scott MacKenzie on 2 Jun 2021
There are a few ways to do this. With annotation, it's easy to combine an arrow with a text box. The downside is you have to use normalized coordinates, rather than data coordinates:
ax = gca;
xValue = 5;
axis([0, 10, 0, 10]);
x2 = xValue / ax.XLim(2) * ax.Position(3) + ax.Position(1);
x1 = x2 - 0.1; % on left side of line
y2 = .5; % middle of line in y-axis
y1 = .5; % middle of line in y-axis
annotation('textarrow', [x1 x2], [y1 y2], 'String', sprintf('x = %d ', xValue));
Scott MacKenzie
Scott MacKenzie on 2 Jun 2021
I tweaked the answer "without knowing the coordinates". Of course, there will be issues if the x value is close to the left side of the plot. You can add some logic, if you wish, to position the text box and arrow on the right or left side of the line depending on the value of x.

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