bamCompare can be used to generate a bigWig or bedGraph file based on two BAM files that are compared to each other while being simultaneously normalized for sequencing depth.
If you are not familiar with BAM, bedGraph and bigWig formats, you can read up on that in our ../help_glossary
The basic algorithm works proceeds in two steps:
- Per-sample scaling / depth Normalization:
- If scaling is used (using the SES or read counts method), appropriate scaling factors are determined to account for sequencing depth differences.
- Optionally scaling can be turned off and individual samples normalized using the RPKM, BPM or CPM methods (or no normalization at all)
- A per-bin calculation is performed after accounting for scaling:
- The genome is transversed and the log2 ratio/ratio/difference/etc. for each bin of fixed width is computed.