align_allele given a data.table of pid,a1,a2 get a list of SNPs where alleles are flipped wrt to basis reference

flip_allele(DT, ref.DT)

Arguments

DT

- a data.table object - columns chr,position,a1 and a2

ref.DT

- a data.table of reference alleles (see details)

Value

an index wrt to DT of OR that require flipping