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Poles of Factors
In Correspondence Analysis each
factor sets up a spatial dimension  that can be represented as an
axis line  whose centre (or barycentre) is the value "0", and that
develops in a bipolar way towards the negative () and positive (+)
end, so that the objects put on the opposite poles are the most
different, almost like the "left" wing and "right" wing on the
political axes.
It is useful to remember what J.P Benzecri, a a
mathematician and one of the most important contributors to this
kind of analysis technique, wrote about it:
"Understanding a factorial axis means finding what is
similar, on the one hand all that is on the right of the origin
(barycentre), on the other all that is on the left of it, and then
expressing concisely and exactly the opposition between the two
extremes". (1984, p. 302, see Bibliography).
N.B.: When factorial graphs are bidimensional
(or tridimensional) the oppositions are more than two: in addition
to left and right, there is up and down. Nevertheless the
interpretation criteria are the same.
