Table 1.

Descriptive statistics of entity types in the National NLP Clinical Challenges (n2c2) data set.

Entity types	Entities, n (%)	Links to 1 drug, n (%)	Links to multiple drugs, n (%)	Maximum number of drug associations
Drug	26,800 (32.57)	—a	—	—
Form	11,010 (13.38)	10,980 (99.56)	48 (<1)	2
Strength	10,921 (13.27)	10,913 (99.70)	33 (<1)	3
Frequency	10,293 (12.51)	10,281 (99.39)	63 (1)	4
Route	8989 (10.92)	9000 (99.08)	84 (1)	4
Dosage	6902 (8.39)	6877 (99.38)	43 (1)	4
Reason	6400 (7.78)	7158 (83.44)	1421 (16.56)	10
Duration	970 (1.2)	991 (92.7)	78 (7)	4

^aNot applicable.