Convert a 4-column genotype matrix or data.frame into a simplified numerical format.
geno.format(X, Y.only = TRUE)A list with elements
Y: A 4-column numeric matrix. Each row is sorted with zeros indicating missing alleles.
A: Vector of allele names.
G: Unique allele combinations, i.e. Y without duplicated rows.
Genotype matrix or data.frame.
Logical. Whether or not to output only Y (see return).