how to calculate degree between 3 points in MATLAB?

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Mahan Soltani
Mahan Soltani 2013-1-1
hi, how can i caculate degree between 3 points? i have position of X and Y of this three points. for more information please see this picture ( http://theme.tk/wp-content/uploads/2013/01/Untitled1.png ) and download this file ( http://theme.tk/wp-content/uploads/2013/01/data.zip ).
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Azzi Abdelmalek
Azzi Abdelmalek 2013-1-1
In your image there are 4 points? Can you be more clear by giving an example of coordinates
Mahan Soltani
Mahan Soltani 2013-1-1
编辑：Mahan Soltani 2013-1-1
yes,but i need degree that is red and (?degree). degree between two line(L-Knee point & Calcaneus) and (Calcaneus & 2th_MT). this image is a motion analys that i need degree of Ankle. some of data is : ( http://theme.tk/wp-content/uploads/2013/01/data-1.zip ) .

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回答（2 个）

Roger Stafford
Roger Stafford 2013-1-1
Let row vectors P0 = [x0,y0], P1 = [x1,y1], and P2 = [x2,y2] be Calcaneus, L-Knee, and 2th_MT points, respectively. The angle shown in red in radians at Calcaneus point is:
ang = atan2(abs(det([P2-P0;P1-P0])),dot(P2-P0,P1-P0));
Multiply by 180/pi to get degrees.
Roger Stafford
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Roger Stafford
Roger Stafford 2013-1-1
No mohammad, I think you had better do that. That last vectorized formula I presented will have to suffice for my contribution to your effort.
Mahan Soltani
Mahan Soltani 2013-1-2
Learning MATLAB on this time is hard and confusing for me. my field is Physical Therapy and i can't uderstand MATLAB very well...

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Image Analyst
Image Analyst 2013-1-1
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Mahan Soltani
Mahan Soltani 2013-1-1
on those post, 2 point are available, but i need 3 point which one of them isn't (0 0 0)! if you see image, you could uderstand...

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