Compare a vector with inferred sibs to a vector of `true' sibs
Vcomp(Infrd, Simld, SNPd)
a named numeric vector of length 4, with the total length of Simld, the length of the intersect of the two vectors, the number occurring in Infrd but not Simld ('err'), and the number occuring in Simld but not Infrd ('missed').
vector of inferred sibs
vector of true sibs
character vector with IDs of genotyped individuals