A pedigree, which is a data frame (id, father/sire, mother/dam, ...). If "sex" is a component, male should be "M", "Male" or 1, and female should be "F", "Female" or 2 (other than 0 and 1). If given, "generation" can be numeric 0, 1, 2, ... or non-numeric "F0", "F1", "F2", ..., which should be in an increasing order. Note: 0 is reserved for unknown father
, mother
or sex
. If a father/mother is an inbred founder, its ID should be tagged by character 'i' (e.g. 1i, 2i, etc.).