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Axial Data Analysis. Random Vector. Axial Data. Properties of Axial data.
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Properties of Axial data Sometime the observations are not direction but axes, that is, the unit vector and – are indistinguishable, so that it is which is observed. In this context it is appropriate to consider probability density functions for onwhich are anitpodally symmetric (diametrically opposite <an antipodal point on a sphere>) • i.e. • in such cases the observations can be regrarded as being on the projective space , which is obtained by identifying opposite points on the sphere .
Random axis Maps to a Projection
Distance .
Watson Distribution • One of the simplest models for axial data is the Dimroth-Scheidegger-Watson model, which has densities • Where Note: the density is rotationally symmetric about
Bingham distribution . Where the integration is with respect to the uniform distribution on