This checks whether the individuals have unique IDs. If not, it creates new IDs by adding the family ID to the indiv. ID. Since the function checks for specific column names, this basically means that the input should be as read from a PED file.
f.check.unique.ids(data.cov)
List with:
ids - new IDs in the same order as "id.c" column in the input data
pedIndex - matrix with "family", "id.child", "id.mother", and "id.father" columns
A matrix with "id.fam", "id.c", "id.m", and "id.f" columns.