Region type for which the coordinates are computed
extend.by
A number between 0 and 1 specifying the percentage by which a region is
extended in order to capture methylation information before region start and after region end
Value
a data frame containing the site index, the assigned region index and the relative coordinate
The relative coordinate is 0 if the site's coordinate is identical to the region start coordinate
and 1 if identical to the regions end coordinate and scaled inbetween. Coordinates can be
less than 0 or larger than 1 if a site is in the upstream or downstream flanking region respectively