def make_feature(fc):
'''Builds a new `StringCounter` from the many `StringCounters` in the
input `fc`. This StringCounter will define one of the targets for
the `MultinomialNB` classifier.
This crucial function decides the relative importance of features
extracted by the ETL pipeline. This is essentially a form of
domain fitting that allows us to tune the extraction to the fields
that are important to a domain. However, if the NER for a domain
is inadequate, then the primary purpose of these relative
weightings is to remove bogus NER extractions.
'''
feat = StringCounter()
rejects = set()
keepers = set()
#keepers_keys = ['GPE', 'PERSON', 'ORGANIZATION', 'usernames']
keepers_keys = ['phone', 'email'] #['usernames', 'phone', 'email', 'ORGANIZATION', 'PERSON']
rejects_keys = ['keywords', 'usernames', 'ORGANIZATION', 'PERSON']
# The features used to pull the keys for the classifier
for f, strength in [('keywords', 10**4), ('GPE', 1), ('bow', 1), ('bowNP_sip', 10**8),
('phone', 10**12), ('email', 10**12),
('bowNP', 10**3), ('PERSON', 10**8), ('ORGANIZATION', 10**6), ('usernames', 10**12)]:
if strength == 1:
feat += fc[f]
else:
feat += StringCounter({key: strength * count
for key, count in fc[f].items()})
if f in rejects_keys:
map(rejects.add, fc[f])
if f in keepers_keys:
map(keepers.add, fc[f])
if u'' in feat: feat.pop(u'')
return feat, rejects, keepers
