Get mapping from lab-site to site
Arguments
- input_ww_data
a dataframe of the wastewater data to be passed
directly to stan, must have the following columns: date, site, lab,
genome_copies_per_ml, site_pop, below_lod, and exclude
Value
a dataframe mapping the unique combinations of sites and labs
to their indices in the model and the population of the site in that
observation unit (lab_site)
