This dataset consists of the substances that make up drugs in the National Drug
Code Directory maintained by the Food and Drug Administration. The original data
was downloaded from https://www.fda.gov/Drugs/InformationOnDrugs/ucm142438.htm.
Each simplex corresponds to an NDC code for a drug, where the nodes are the
substances that make up that drug. Timestamps are in days and represent when the
drug was first marketed.

The file NDC-substances-node-labels.txt maps the node IDs to the substances.

The nth line in NDC-classes-simplex-labels.txt is the name of the drug
corresponding to the nth simplex.