Create model for dissecting the sig field into computable structured data

[cgreich]

This is a placeholder, so a proposal could be worked out:

Instead of the free text sig field (which may even be in a non-English language), we need to have the actual frequency information. So, 2 mL tablets 3 times a day" would become something like:

sig_amount - numeric (2) sig_unit_concept_id - concept (concept_id for liquid units, most often "mL") frequency - numeric (3) frequency_unit_concept_id - concept (concept_id for "day")