-------- Original Message --------
Subject: Re: Calculating angles from landmarks
Date: Fri, 5 Nov 2010 15:50:10 -0400
From: Dennis E. Slice <[email protected]>
To: [email protected]
The old Morpheus et al. will calculate the angle between three points.
For intersection of lines defined by two pairs of points, just subtract
the coordinates of one of the point pair from the other - this will make
the two line segments vectors from the origin. Then the angle between
those vectors is the same as the angle between the lines and can be
computed from:
cos(theta) = (x1*x2 + y1*y2) / sqrt((x1*x1+y1*y1)(x2*x2+y2*y2))
or
theta = arccos( (x1*x2 + y1*y2) / sqrt( (x1*x1+y1*y1)*(x2*x2+y2*y2) ) )
where xi,yi are the x and y coordinates of the ith vector created above,
and the formula is just, in using dot, "a dot b over the square root of
a dot a times b dot b" where a and b are the vectors created above.
-ds
On 11/5/10 2:44 PM, morphmet wrote:
-------- Original Message --------
Subject: Calculating angles from landmarks
Date: Fri, 5 Nov 2010 11:57:30 -0400
From: Thomas O'Mahoney <[email protected]>
To: [email protected]
Dear List,
I was wondering if anyone would be able to point me in the right
direction of how to do this.
I am looking at investigating torsion in longbones as part of a
morphometric analysis. How would one go about calculating the angle
between 2 sets of two landmarks in the x-z plane? The lines would
obviously cross.
Is there a piece of code out there that will do this, or a function in
morphometrics software?
Many thanks,
Tom O'Mahoney
PhD Student
Department of Archaeology
University of Sheffield
[email protected] <mailto:[email protected]>
[email protected] <mailto:[email protected]>
--
Dennis E. Slice
Associate Professor
Dept. of Scientific Computing
Florida State University
Dirac Science Library
Tallahassee, FL 32306-4120
-
Guest Professor
Department of Anthropology
University of Vienna
-
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