/
vectors.py
286 lines (232 loc) · 8.45 KB
/
vectors.py
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"""
Vector processing API.
$Id: vectors.py,v 1.2 2008/12/04 12:29:57 lars.garshol Exp $
"""
import math, chew, string, langmodules
class Vector:
"A term vector."
def __init__(self, vector = None):
self._vector = vector or {}
def add_term(self, term):
self._vector[term] = self._vector.get(term, 0) + 1
def get_keys(self):
return self._vector.keys()
def get(self, key, default = None):
return self._vector.get(key, default)
def get_pairs(self):
return self._vector.items()
def get_count(self, term):
return self._vector.get(term, 0)
def get_map(self):
return self._vector
def cosine(self, other):
topsum = 0
for (term, count) in self.get_pairs():
topsum += count * other.get_count(term)
botsum1 = 0
for (term, x) in self.get_pairs():
botsum1 += x * x
botsum2 = 0
for (term, y) in other.get_pairs():
botsum2 += y * y
if not botsum1 * botsum2:
return 0
else:
return topsum / (math.sqrt(botsum1) * math.sqrt(botsum2))
def display_comparison(self, other, showall = 0):
terms = {}
for (term, count) in self.get_pairs():
terms[term] = count * other.get_count(term)
termlist = chew.sort(terms.items(), lambda x: x[1])
termlist.reverse()
for (term, score) in termlist:
if score:
print (term, score)
if showall:
list = []
for (term, count) in self.get_pairs():
if not terms.get(term, 0):
list.append(term.encode("utf-8"))
print "+", string.join(list, ", ")
list = []
for (term, count) in other.get_pairs():
if not terms.get(term, 0):
list.append(term.encode("utf-8"))
print "-", string.join(list, ", ")
def dump(self):
list = self._vector.items()
list = chew.sort(list, lambda x: x[1])
list.reverse()
for (term, count) in list:
print term.encode("utf-8"), count
print "Terms:", len(self._vector)
def normalize(self, tracker):
v = {}
for (term, val) in self._vector.items():
v[term] = tracker.get_score(term, val)
self._vector = v
class Cluster:
def __init__(self, members = None):
self._members = []
if members:
for member in members:
self.add(member)
self._average = 0
self._name = None
def set_name(self, name):
self._name = name
def get_name(self):
return self._name
def get_members(self):
return self._members
def clear_members(self):
self._members = []
def add(self, vector):
if isinstance(vector, Vector):
self._members.append(vector)
else:
self._members.append(vector.get_vector())
self._average = None
def make_average_vector(self):
if not self._members:
self._average = Vector({})
return
if len(self._members) == 1:
self._average = self._members[0]
average = {}
for member in self._members:
for (term, count) in member.get_pairs():
average[term] = count + average.get(term, 0)
mc = float(len(self._members))
for term in average.keys():
average[term] = average[term] / mc
self._average = Vector(average)
def get_average_vector(self):
if not self._average:
self.make_average_vector()
return self._average
def compare(self, other):
return self.get_average_vector().cosine(other.get_average_vector())
def __repr__(self):
return repr(self._members)
def k_nearest_neighbours_2(objects):
"""Makes clusters of objects. All objects must implement
object.compare(other), object.get_key(), and object.get_name()."""
pairs = []
for ix in range(len(objects)):
for i in range(ix+1, len(objects)):
pairs.append((objects[ix],
objects[i],
objects[ix].compare(objects[i])))
pairs = chew.sort(pairs, lambda x: x[2])
pairs.reverse()
clusters = []
clustermap = {}
for (t1, t2, score) in pairs:
if not score or (clustermap.has_key(t1.get_key()) and
clustermap.has_key(t2.get_key())):
if score:
pass #print "NOT USING:", (t1, t2, score)
continue
print (t1.get_name(), t2.get_name(), score)
#compare(get_matrix(t1, terms), get_matrix(t2, terms))
if clustermap.has_key(t1.get_key()):
c = clustermap[t1.get_key()]
elif clustermap.has_key(t2.get_key()):
c = clustermap[t2.get_key()]
else:
c = Cluster()
clusters.append(c)
for t in (t1, t2):
if not clustermap.has_key(t.get_key()):
c.add(t)
clustermap[t.get_key()] = c
return clusters
def update(compcache, c1, c2, score):
c1 = id(c1)
c2 = id(c2)
if compcache.has_key(c1):
compcache[c1][c2] = score
else:
compcache[c1] = {c2 : score}
def merge_cluster(objects, debug = 1):
"""Makes clusters of objects. All objects must implement
object.get_key(), object.get_name(), and object.get_vector()."""
# make one cluster for each object
clusters = map(lambda x: Cluster([x]), objects)
print len(clusters)
stop = int(math.log(len(clusters)) * 7)
# using this changes the algorithm from n**3 to n**2
compcache = {} # id(cluster) -> {id(cluster) : comp, id(cluster) : comp...}
for ix in range(len(clusters)):
for i in range(ix+1, len(clusters)):
if ix != i:
score = clusters[ix].compare(clusters[i])
update(compcache, clusters[ix], clusters[i], score)
update(compcache, clusters[i], clusters[ix], score)
while len(clusters) > stop:
# find closest pair
highest = 0
pair = None
for ix in range(len(clusters)):
for i in range(ix+1, len(clusters)):
if ix != i:
score = compcache[id(clusters[ix])][id(clusters[i])]
if score > highest:
pair = (clusters[ix], clusters[i])
highest = score
# merge the pair
print pair
clusters.remove(pair[0])
clusters.remove(pair[1])
del compcache[id(pair[0])]
del compcache[id(pair[1])]
nc = Cluster(pair[0].get_members() + pair[1].get_members())
for ix in range(len(clusters)):
score = clusters[ix].compare(nc)
update(compcache, clusters[ix], nc, score)
update(compcache, nc, clusters[ix], score)
clusters.append(nc)
print len(clusters), stop
return clusters
class WordFrequencyTracker:
def __init__(self):
self._words = {}
self._total = 0
def add_occurrence(self, word):
self._words[word] = self._words.get(word, 0) + 1
self._total += 1
def get_score(self, term, val):
count = self._words.get(term, 0)
if count <= 4:
return 0
factor = count / float(self._total)
return math.log(val / factor)
def get_count(self, term):
return self._words.get(term, 0)
def print_report(self):
print "TOTAL COUNT:", self._total
items = chew.sort(self._words.items(), lambda x: x[1])
items.reverse()
for (term, count) in items[ : 20]:
print "%30s %s" % (term.encode("utf-8"), count)
print "..."
for (term, count) in items[-20 : ]:
print "%30s %s" % (term.encode("utf-8"), count)
def text_to_vector(text, blacklist = {}, tracker = None, stemming = 0):
termlist = chew.extract_terms(text)
lang = langmodules.get_language_module(termlist)
vector = Vector()
for term in termlist:
term = string.lower(term)
if chew.acceptable_term(term) and \
not lang.is_stop_word(term) and \
not blacklist.has_key(term):
if stemming:
stem = lang.get_stem(term)
else:
stem = term
if tracker:
tracker.add_occurrence(stem)
vector.add_term(stem)
return vector