Case-insensitive test for taxa starting with 'azoi'
is_azoic(x)logical vector, with elements TRUE for azoic samples,
and FALSE otherwise.
character vector containing taxa
Azoic samples need special attention during data analysis. They should be marked as 'azoic', and taken care of during analysis. Note that an azoic sample is not the same as a record where a taxon has zero counts. The latter should be removed from further analysis, whereas the former provides important information.