Calculates and visualises cumulative percent 'decay' curves,
which are typically calculated from metagenomic taxonomic profiles.
These can be used to estimate the level of expected 'endogenous' taxa
at different abundance levels retrieved from metagenomic samples, when
comparing to samples of known sampling site or source. Method
described in Fellows Yates, J. A. et. al. (2021) Proceedings of the
National Academy of Sciences USA