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 bi-dimensional (or tri-dimensional) the oppositions are more than two: in addition to left and right, there is up and down. Nevertheless the interpretation criteria are the same.