How MetaPhlAn calculates relative abundance

Question

[dpc]

Hi there!!! Can anyone please simply tell me how metaphlan calculates relative abundance of the taxa? After reading these and these answers I am really confused with the process. Earlier I thought it is just (number of reads of a bug / total number of reads of all bugs). But it's not like that.

A simplified answer will be highly appreciated.

Best, DC7

Answer 1

[plicht]

I guess the answer here is (#reads of a bug mapping to marker / (size of clade_marker / clade_genome_size) * #total reads). But I am also confused by this. A clear equation would be nice.