vector of two allele codes (usually characters), or
NA.
allelepair2
vector of two allele codes (usually characters), or
NA.
method
one of "sum" or "geometrical".
Value
If method=="sum", number of shared alleles (0, 1 or 2), or
NA. If method=="geometrical", 0, 0.5, sqrt(0.5)
(in case that one of the allelepairs is double such as in
c("A","B"),c("A","A")) or 1, or
NA.