Create and return a dataframe of ped.id, person1.id, person2.id, and ibd information from merlin
ibd.df.merlin(ibd.dat)
The returned data.frame, call it df, with the following elements:
pedigree id
person 1 of a relative pair
person 2 identifier of a relative pair within a pedigree
matrix objects that can be referenced from df. Each
is a matrix with posterior ibd sharing probabilities for
relative pairs (rows) at each chromosome position (columns)
data.frame with posterior IBD data from Merlin, with column names: FAMILY, ID1, ID2, MARKER