Package indexsplit is used to quickly generate evenly sized (by amount of data) regions across a cohort. It does this by reading the bam (or cram) index and using the file offsets as proxies for the amount of data. It sums the values in these bins across all samples. This gives a good estimate for actual reads in the region but without having to parse the bam file.
A common use of this will be to generate regions to be use to parallelize variant calling fairly by splitting in to `N` regions with approximately equal amounts of data **across the cohort**.