plot.circumplex_cpm: Plot a circular process model fit
Description
Draw the estimated item configuration of a cpm_fit() object on the circular
canvas from ggcircumplex(). Each scale is placed at its estimated angle
(\(\theta\)), at a radius given by its communality
(\(\zeta^2\), the share of
its variance explained by the common circumplex factors), so items that the
model explains well sit near the outer ring and items it explains poorly sit
near the centre. The canvas spokes mark the theoretical angles supplied to
cpm_fit(), so the gap between a point and its spoke shows how far the
estimated angle departed from the hypothesised one. Where the confidence
intervals are estimable, a wedge spans each item's angle CI (angularly) and
communality CI (radially).