def _set_ratios(self):
self._set_partofspeech_ratios()
self._set_base_ratios()
self._set_group_ratios()
self.wordclass_model.log_methods()
self.wordclass_model = FlatModel(self.wordclass_model)
calibrator = Calibrator(self.wordclass_model, self.ngram_manager)
if calibrator.is_viable():
self.calibrator = calibrator
def __init__(self, **kwargs):
self.wordform = kwargs.get('form', None)
self.lex_items = kwargs.get('lex_items', [])
self.ngram = kwargs.get('ngram', None)
self.ngram_manager = NgramSetManager(self.ngram,
kwargs.get('tagged_ngrams', []))
self.wordclass_model = HierarchicalModel(self.lex_items,
self.wordform)
self.corpus_probability_sets = {
'bnc': CORPUS_MANAGERS['bnc'].find(self.wordform),
'oec': CORPUS_MANAGERS['oecpos'].find(self.wordform),
'oec_lempos': _find_oec(self.lex_items),
}
self.calibrator = None
self._set_ratios()
class WordclassRatios(object):
"""
Manage the way that an overall ngram score (for the main untagged
ngram) is subdivided between different parts of speech, e.g. between
impact n. and impact v.
There are four possible methods:
1. base subdivision on ratios found in OEC pos tables
2. base subdivision on ratios found in BNC pos tables
3. base subdivision on ratios found in OEC lempos tables
4. base subdivision on predicted frequency
(1/2) is used if the OEC/BNC tables cover all the right
parts of speech; failing that, (3) is used if the OEC lempos
tables cover all the right parts of speech; failing that,
(4) is used.
Special handling ('verblike') for cases where there's a VBG or VBN
and JJ or NN: these can be handled by the BNC method, but can't be
usefully handled by any of the other methods.
"""
def __init__(self, **kwargs):
self.wordform = kwargs.get('form', None)
self.lex_items = kwargs.get('lex_items', [])
self.ngram = kwargs.get('ngram', None)
self.ngram_manager = NgramSetManager(self.ngram,
kwargs.get('tagged_ngrams', []))
self.wordclass_model = HierarchicalModel(self.lex_items,
self.wordform)
self.corpus_probability_sets = {
'bnc': CORPUS_MANAGERS['bnc'].find(self.wordform),
'oec': CORPUS_MANAGERS['oecpos'].find(self.wordform),
'oec_lempos': _find_oec(self.lex_items),
}
self.calibrator = None
self._set_ratios()
def find_ratios(self, wordclasses, year):
"""
Derive the appropriate set of ratios for each decade.
"""
ratios = {}
# Shortcut in case of just a single wordclass
if len(self.wordclass_model.full_set_of_wordclasses()) <= 1:
for w in wordclasses:
ratios[w] = 1.0 / len(wordclasses)
for lex_item in self.lex_items:
lex_item.wordclass_method = 'singleton'
return ratios
else:
if self.calibrator:
calibrated_value = self.calibrator.calibrate(year)
self.wordclass_model.inject_calibration(calibrated_value)
for w in wordclasses:
ratios[w] = self.wordclass_model.pos_ratio(w)
if not 'NP' in ratios and self.wordclass_model.pos_ratio('NP') > 0:
ratios['NP'] = self.wordclass_model.pos_ratio('NP')
return adjust_to_unity(ratios)
def _set_ratios(self):
self._set_partofspeech_ratios()
self._set_base_ratios()
self._set_group_ratios()
self.wordclass_model.log_methods()
self.wordclass_model = FlatModel(self.wordclass_model)
calibrator = Calibrator(self.wordclass_model, self.ngram_manager)
if calibrator.is_viable():
self.calibrator = calibrator
def _set_partofspeech_ratios(self):
"""
Establish ratios for specific parts of speech (lowest
level of the wordclass model, below base wordclasses)
Note that OEC lempos probabilities can't be used here, since
the OEC lempos tables are not granular enough (they only give
probabilities for base wordclasses, not for specific parts
of speech)
"""
for group in self.wordclass_model.model().values():
for base in group.model().values():
method_type = None
ratio_set = dict()
if len(base.model()) == 1:
for pos in base.model().keys():
ratio_set[pos] = 1.0
method_type = 'singleton'
if not method_type:
for corpus in ('oec', 'bnc'):
probability_set = self.corpus_probability_sets[corpus]
if (probability_set and
probability_set.covers(base.full_set_of_wordclasses())):
for pos in base.model().keys():
ratio_set[pos] = probability_set.ratio(pos)
method_type = corpus
break
if not method_type:
for pos, item in base.model().items():
ratio_set[pos] = item.predicted_frequency()
method_type = 'predictions'
if ('NP' in base.model() and
'NN' in base.model() and
len(base.model().keys()) == 2):
ratio_set = self._np_adjuster(base.model(), ratio_set)
ratio_set = adjust_to_unity(ratio_set)
base.set_ratios(ratio_set, method_type)
def _set_base_ratios(self):
"""
Set ratios for base wordclasses within each group.
Based on measured or predicted frequencies.
"""
for group in self.wordclass_model.model().values():
method_type = None
ratio_set = {}
# No need to bother when there is only one wordclass (singleton)
if len(group.model()) == 1:
for wc in group.model().keys():
ratio_set[wc] = 1.0
method_type = 'singleton'
if not method_type:
# Take ratios from OEC/BNC pos, if it's available and covers
# the right set of wordclasses
for corpus in ('bnc', 'oec'):
probability_set = self.corpus_probability_sets[corpus]
if (probability_set and
probability_set.covers(group.base_set_of_wordclasses(), base=True)):
for wc in group.model().keys():
ratio_set[wc] = probability_set.base_ratios()[wc]
method_type = corpus
break
if not method_type:
# Take ratios from OEC/BNC pos, if it's available and covers
# *nearly* the right set of wordclasses. If a minor wordclass
# is not covered, use an estimate for this.
for corpus in ('bnc', 'oec'):
probability_set = self.corpus_probability_sets[corpus]
if (probability_set and
probability_set.almost_covers(group.base_set_of_wordclasses())):
missing = probability_set.almost_covers(group.base_set_of_wordclasses())
est = self._estimate_missing(missing=missing,
corpus=corpus,
model=group.model())
if est is not None:
# Set the ratios of the wordclasses that *are* covered
for wc in group.base_set_of_wordclasses():
if wc != missing:
ratio_set[wc] = probability_set.base_ratios()[wc]
# Use estimate as the ratio of the missing wordclass
ratio_set[missing] = est
method_type = corpus
break
if not method_type:
# Take ratios from OEC lempos, if it's available and covers
# the right set of wordclasses
probability_set = self.corpus_probability_sets['oec_lempos']
if (probability_set and
probability_set.covers(group.base_set_of_wordclasses(), base=True) and
not group.is_verblike()):
for wc in group.model().values():
ratio_set[wc.wordclass] =\
probability_set.sum_subcategories(list(wc.model().keys()))
method_type = 'oeclempos'
if not method_type:
# Take ratios from OEC lempos, if it's available and covers
# *nearly* the right set of wordclasses. If a minor wordclass
# is not covered, use an estimate for this.
probability_set = self.corpus_probability_sets['oec_lempos']
if (probability_set and
probability_set.almost_covers(group.base_set_of_wordclasses()) and
not group.is_verblike()):
missing = probability_set.almost_covers(group.base_set_of_wordclasses())
est = self._estimate_missing(missing=missing,
trace=False,
corpus='oec',
model=group.model())
if est:
# Set the ratios of the wordclasses that *are* covered
for wc in group.base_set_of_wordclasses():
if wc != missing:
ratio_set[wc] = probability_set.base_ratios()[wc]
# Use estimate as the ratio of the missing wordclass
ratio_set[missing] = est
method_type = 'oeclempos'
# Fall back on predictions
if not method_type:
for wc, item in group.model().items():
ratio_set[wc] = item.predicted_frequency()
ratio_set = _crosscheck(ratio_set, group.model())
method_type = 'predictions'
ratio_set = adjust_to_unity(ratio_set)
group.set_ratios(ratio_set, method_type)
def _set_group_ratios(self):
"""
Set ratios for main groups
Based on measured or predicted frequencies.
Groups are either 'core' (NN + VB + JJ) or 'other' (everything else)
"""
method_type = None
if len(self.wordclass_model.model()) == 1:
ratio_set = {grp: 1.0 for grp in self.wordclass_model.model().keys()}
method_type = 'singleton'
if not method_type:
probability_set = self.corpus_probability_sets['bnc']
if (probability_set and
self.wordclass_model.groupset() == probability_set.groupset()):
ratio_set = {grp: probability_set.group_ratios()[grp]
for grp in self.wordclass_model.groupset()}
method_type = 'bnc'
if not method_type:
probability_set = self.corpus_probability_sets['oec_lempos']
if (probability_set and
self.wordclass_model.groupset() == probability_set.groupset() and
probability_set.covers(self.wordclass_model.base_set_of_wordclasses(), base=True) and
probability_set.sum_ratios(self.wordclass_model.base_set_of_wordclasses()) > 0.9):
ratio_set = {grp: probability_set.group_ratios()[grp]
for grp in self.wordclass_model.groupset()}
method_type = 'oeclempos'
if not method_type:
ratio_set = {pos: item.predicted_frequency() for pos, item
in self.wordclass_model.model().items()}
ratio_set = _crosscheck(ratio_set, self.wordclass_model.model())
method_type = 'predictions'
ratio_set = adjust_to_unity(ratio_set)
self.wordclass_model.set_ratios(ratio_set, method_type)
def method(self):
return self.wordclass_model.method()
def _estimate_missing(self, **kwargs):
"""
If all but one of the wordclasses are accounted for by the
corpus probability set, and the missing wordclass appears
to be minor (based on predicted frequency), then we'll just
estimate the missing wordclass.
This is most likely to capture VBG+JJ+NN sets where either
the JJ or NN is missing in BNC. May also capture
some VBN+JJ+NN sets, where the NN is vanishingly rare.
"""
missing = kwargs.get('missing')
model = kwargs.get('model')
corpus = kwargs.get('corpus', 'bnc').lower()
trace = kwargs.get('trace', False)
# The missing item has to have a predicted frequency ratio
# below this threshold
if corpus == 'bnc':
threshold = 0.2
elif corpus == 'oec':
threshold = 0.1
# How significant is the missing wordclass, as a proportion of
# the total predicted frequencies? The ratio needs to be low, in
# order for it to be plausible that it's missing from the BNC data
sum_predictions = sum([b.predicted_frequency()
for b in model.values()])
if sum_predictions:
predicted_ratio = model[missing].predicted_frequency()\
/ sum_predictions
else:
predicted_ratio = 1
if trace:
print('-------------------------------------------------')
print(self.wordform)
print('\t%s:' % corpus.upper())
probability_set = self.corpus_probability_sets[corpus]
for wordclass, f in probability_set.base_ratios().items():
print('\t\t%s\t%0.3g' % (wordclass, f))
print('\tpredictions:')
for b in model.values():
print('\t\t%s\t%0.3g' % (b.wordclass, b.predicted_frequency()))
if predicted_ratio < threshold:
print('---> %s = %0.3g' % (missing, predicted_ratio))
else:
print('FAILED (%s = %0.3g)' % (missing, predicted_ratio))
print('-------------------------------------------------')
if predicted_ratio < threshold:
return predicted_ratio
else:
return None
def _np_adjuster(self, model, ratio_set):
"""
Where a set consists of NN and NP, make sure that the NN is
not scoring artificially high.
If the NN's calculated score (based on the ratio already derived)
is higher than its predicted frequency (based on size), then the
ratio is recalculated from the NN's predicted frequency.
"""
ratio_set = adjust_to_unity(ratio_set)
ngram_total = self.ngram.frequency('1970-2000')
nn_freq_calculated = ngram_total * ratio_set['NN']
nn_freq_predicted = model['NN'].predicted_frequency()
if nn_freq_predicted < nn_freq_calculated:
nn_revised_ratio = nn_freq_predicted / ngram_total
ratio_set = {'NN': nn_revised_ratio, 'NP': 1 - nn_revised_ratio}
return ratio_set
