how to automatically find the angle from 2 points ?

I try to find the angle between 2 points that I manual put it in the image but I want to find the angle between this 2 points with automatically methods.

How to do ? Thank you.

[Akira Agata]

You mean, angle between 1) the line connecting two markers and 2) horizontal line, like the following ?

[Allen]

What Akira is pointing out is that you cannot form an angle with two points, which only forms a single line. You need a second line to form angle (ie - a horizontal line as a reference).

A method that you can use is to capture the mouse position when clicking and after selecting two locations and then calculating the angle between the imagined line between those two points and a horizontal line. I am not able to directly help you with that step, however, the following function posted to File Exchange uses the mouse position capture capability for which you can deduce how to use from the code.

https://www.mathworks.com/matlabcentral/fileexchange/5961-magnify

[wongsathorn pinwihok]

I'm sorry. I mean what you said Akira.

[wongsathorn pinwihok]

how can i define that 2 markers and find the angles like Akira said?

[Adam Danz]

If point1 and point2 are defined by (x1,y1), (x2,y2), you can get the angle by

atan(abs(y2-y1)/abs(x2-x1))  % radians
% or
atand(abs(y2-y1)/abs(x2-x1)) % degrees

If you want to programmatically define the two points as well you'll have quite a bit more work to do starting with a solid definition of how they are located.