Substitution mapping and measures of coevolution. For the sake of simplicity, ancestral state uncertainty is not taken into account in this figure. True substitution vectors are averaged over all possible ancestral states. a) Unweighted (V), weighted (V*) and signed, weighted () substitution mapping, according to volume (vol), polarity (pol) and charge (cha). b) Coevolution measures for a pair of sites: correlation coefficient on the simple vectors, correlation coefficient on the volume-weighted unsigned vectors, and compensation index on the volume-weighted signed vectors.