----- Forwarded message from Marlijn Noback
<[email protected]> -----
Date: Thu, 7 Mar 2013 05:52:18 -0500
From: Marlijn Noback <[email protected]>
Reply-To: Marlijn Noback <[email protected]>
Subject: Compare Vector Directions?
To: [email protected]
Dear all,
With enthusiasm I have tried the feature of vector direction
comparison within MorphoJ. But there is something I do not understand.
I sincerly hope you can help me with this issue. I am new to this
analysis, so I am not sure how to interpret my data.
I am trying to see if some of the environmental factors I am analyzing
have similar effects on cranial shape as do changes in cranial size.
I compared the following vectors:
Regression of shape on factor A, B, C, D and E.
Regression of shape on centroid size.
And it gave me the following results:
Angles (in degrees)
CentSize1
Fac.A 148.621
Fac.B 32.194
Fac.C 64.088
Fac.D 76.127
Fac.E 130.435
P-values (parametric)
CentSize1
Fac.A 1.00000
Fac.B <.00001
Fac.C 0.00433
Fac.D 0.08267
Fac.E 0.99999
Why is a 30 degrees angle showing a significant P value (0.0001), but
a 150 degrees angle a P value of 1 ? I thought 150 degree angle is
actually like 30 degrees, but then with the vectors having opposite
signs?
So that vectors with a 150 degree angle between them would still be
more similar to each other (but with opposite signs) than vectors that
have an angle of 90 degrees between them?
In my opinion, the relation between Factor B and shape is very similar
to centroid size effects, as is Factor A, although in opposite
direction.
All other factors have a different relation to shape.
Is this the correct interpretation?
I would very much appreciate your help in this.
With kind regards,
Marlijn Noback
marlijn.noback ( at ) ifu.uni-tuebingen.de
----- End forwarded message -----
