This is an unexported helper used in in ibd2kin. The function interpolates over segments to apply genetic length to the segment. It is inspired by Python code distributed by the Browning lab (documentation).
interpolate(ibd_bp, chromgpos)Base pair for the IBD segment over which to interpolate
Genetic map data for a specific chromosome
Numeric vector with the genetic distance shared at the segment.
http://faculty.washington.edu/sguy/ibd_relatedness.html