def gen_counts(input_path, output_path):
if exists(output_path): return
print 'Generating counts from: "%s"' % input_path
counter = Hmm(3)
counter.train(open(input_path, 'r'))
counter.write_counts(open(output_path, 'w'))
def gen_counts(input_path, output_path):
if exists(output_path): return
print 'Generating counts from: "%s"' % input_path
counter = Hmm(3)
counter.train(open(input_path, 'r'))
counter.write_counts(open(output_path, 'w'))
###################################################
###################################################
print("\n2. Generate word count file.\n")
freqs_input = open('gene.replace.train',"r")
freqs_output = open('gene.counts', "w")
# Initialize a trigram counter
counter = Hmm(3)
# Collect counts
counter.train(freqs_input)
# Write the counts
counter.write_counts(freqs_output)
freqs_output.flush()
###################################################
###################################################
print("\n3. Tag dev corpus with Viterbi tagger.\n")
v_counts_file = open('gene.counts',"r")
class Tagger(object):
def __init__(self, infile="ner_train.dat"):
self.counter = Hmm(3)
with open(infile) as f:
self.counter.train(f)
self.unigrams = {k[0]:v for k,v in self.counter.ngram_counts[0].iteritems()} #since the key is a one-word tuple
self.bigrams = self.counter.ngram_counts[1]
self.trigrams = self.counter.ngram_counts[2]
self.words = [x[0] for x in self.counter.emission_counts.keys()]
"""
conditional probability that the word maps to tag given the number of times the tag occurs
"""
def compute_emission(self, word, tag):
em = self.counter.emission_counts
if tag == '*':
return 0
if (word,tag) in em:
return em[(word,tag)]/float(self.unigrams[tag])
elif word in self.words:
return 0
else:
return em[('_RARE_',tag)]/float(self.unigrams[tag])
"""
returns the trigram count over the bigram count, defaulting the dict gets so that there aren't division by 0 errors
"""
def compute_trigram(self,yi,y1,y2):
return self.trigrams.get((y2,y1,yi),0)/float(self.bigrams.get((y2,y1),1))
"""
basic file replacement, writes to a new file called rare-{infile} where infile is provided. Can pass a threshold of how many common_words
is considered "rare"
"""
def replace_rare(self,infile,threshold=5):
wordcounts = defaultdict(int)
for tup in self.counter.emission_counts.iteritems():
wordcounts[tup[0][0]] += tup[1] # aggregates counts of words total, with any tag
common_words = [k for k,v in wordcounts.iteritems() if v >= threshold]
replaced = 0
f = open(infile)
f2 = open(infile.replace('.dat','-rare.dat'), 'w')
for line in f:
if len(line.split(' ')) == 2:
if line.split(' ')[0] not in common_words: # closed set, there are more rare than not rare, we know it's one or the other
f2.write(line.replace(line.split(' ')[0], '_RARE_', 1))
replaced +=1
else:
f2.write(line)
else:
f2.write(line) # maintain stops
f.close()
f2.close()
"""
returns a dictionary of relative probabilities for emission counts
"""
def tag_probabilities(self,word):
counts = {tag:self.compute_emission(word,tag) for tag in self.unigrams}
prob = lambda v: v/sum(counts.values()) if sum(counts.values()) != 0 else 0
return {k:prob(v) for k,v in counts.iteritems()}
"""
wrapper function for dynamic programming algorithm, writes to outfile
"""
def viterbi(self,infile,outfile):
def write_to_pred_file(f,sentence):
tag_seq = [" ".join(x) for x in self.tag_sequence(sentence)] #tuples of tag,probability
for word,tag in itertools.izip(sentence,tag_seq): # word, tag, probability
f.write('%s %s\n' % (word,tag))
f.write('\n')
with open(infile) as f, open(outfile,"w") as f2:
sentence = []
for line in f:
if line == '\n':
write_to_pred_file(f2,sentence)
sentence = []
continue
else:
sentence.append(line.strip())
#write the last sentence to the file (if there is no newline -- will just return and escape if sentence is empty
write_to_pred_file(f2,sentence)
def tag_sequence(self,sentence):
if len(sentence) == 0:
return []
possible_tags = self.unigrams.keys()
possible_tags.append('*')
bp = {i:{} for i in range(len(sentence) + 1)}
# initialization: pi(0,'*','*') = 1, pi(0,u,v) = 0
bp[0] = {t:('O',0) for t in itertools.product(possible_tags,repeat=2)}
bp[0][('*','*')] = (1.0,1.0)
# at idx 1, u can only be *
for v in possible_tags:
tag_max = ('sentinel',-1) #a real probability (since logs are only computed at end) will never be negative, so this will be reset
tags = {}
for w in possible_tags:
tags[w] = bp[0][(w,'*')][1]*self.compute_trigram(v,w,'*')*self.compute_emission(sentence[0],v)
if tags[w] > tag_max[1] and tags[w] != 0:
tag_max = (w,tags[w])
bp[1][('*',v)] = tag_max if tag_max != ('sentinel',-1) else ('O',0) #default tag is no tag, so O -- no sequences with this u,v with a nonzero probability
for i,word in enumerate(sentence[1:], start=2): #from 2...n
for v,u in itertools.product(possible_tags,repeat=2): #same as nested for u in K, v in K
tag_max = ('sentinel', -1)
tags = {}
for w in possible_tags:
if (w,u) in bp[i-1]:
tags[w] = bp[i-1][(w,u)][1]*self.compute_trigram(v,u,w)*self.compute_emission(word,v)
if tags[w] > tag_max[1] and tags[w] != 0:
tag_max = (w,tags[w])
bp[i][(u,v)] = tag_max if tag_max != ('sentinel',-1) else ('O',0)
n = len(sentence)
last = {(u,v): bp[n][(u,v)][1]*self.compute_trigram('STOP',v,u) for u,v in bp[n].keys()}
yn1,yn = max(last, key=last.get) # max probability for sequence ending in STOP
conf = last[(yn1,yn)]
seq = [(yn,str(ln(conf))), (yn1,str(ln(conf)))] #sequence will be yn...y0
for i in xrange(len(sentence) - 2, 0, -1):
u,v = tuple(x[0] for x in reversed(seq[-2:])) #previous two are yn-1, yn-2
prev = bp[i+2][(u,v)]
seq.append((prev[0], str(ln(prev[1]))))
return reversed(seq) #reversed yn...y0 is y0...yn
def train_ngram_and_emission_freq_from_corpus_file(self, corpus_file):
counter = Hmm(3)
counter.train(corpus_file)
self.emission_counts = counter.emission_counts
self.ngram_counts = counter.ngram_counts
else:
return "I-GENE"
def get_rare_words(d):
temp_d = d.copy()
O_words, GENE_words = set(), set()
for key, value in d.iteritems():
if value < 5 and get_max_value(temp_d, key[0]) < 5:
if get_most_tag(temp_d, key[0]) == "O":
O_words.add(key[0])
else:
GENE_words.add(key[0])
return (O_words, GENE_words)
if __name__ == "__main__":
counter = Hmm(3)
counter.train(file("data/gene.train","r"), RARE=False)
# print counter.emission_counts
rare_words = get_rare_words(counter.emission_counts)
# print len(rare_words[0]) #O_words = 19034
# print len(rare_words[1]) #GENE_words = 6231
with open("data/rare_words.pickle", "wb") as f:
pickle.dump(rare_words, f)
