def __init__(self, x, y, min_word_length=0, min_word_freq=0, num_of_features_of_each_class=100, sw=True):
self.weights = {'tf', 'tfidf'}
self.num_of_docs = len(x)
self.classes = set(y)
word_count = self.read_in_all_words(x, min_word_length, min_word_freq, sw)
self.class_word_count = self.get_class_word_count(x, y, word_count)
self.features = self.select_features(word_count, self.class_word_count, num_of_features_of_each_class)
self.x_le = LabelEncoder().fit(self.features)
self.y_le = LabelEncoder().fit(y)
class Features:
def __init__(self, x, y, min_word_length=0, min_word_freq=0, num_of_features_of_each_class=100, sw=True):
self.weights = {'tf', 'tfidf'}
self.num_of_docs = len(x)
self.classes = set(y)
word_count = self.read_in_all_words(x, min_word_length, min_word_freq, sw)
self.class_word_count = self.get_class_word_count(x, y, word_count)
self.features = self.select_features(word_count, self.class_word_count, num_of_features_of_each_class)
self.x_le = LabelEncoder().fit(self.features)
self.y_le = LabelEncoder().fit(y)
def read_in_all_words(self, x, min_word_len=0, min_to_count=0, sw=True):
"""
Get all vocabularies that can be the feature
:param x: A list of files to read.
:return: A set of under_conditions_words that contained in x
"""
stopwords.add("") # to remove empty word
vocabularies = Counter() # Count the vocabularies
voc = Counter() # the vocabularies that we finally need
for name in x:
file = open(name, 'r', errors='ignore') # There's some decoding errors
word_mark = set() # Mark if the word has been count
for line in file:
for word in r.split(line): # strip the punctuation
word = word.lower() # lower case
if (not sw or word not in stopwords) and len(word) >= min_word_len: # ignore the words that too short
if word not in vocabularies:
vocabularies[word] = [1, 1]
word_mark.add(word)
else:
vocabularies[word][0] += 1
vocabularies[word][1] += 1 if word not in word_mark else 0
if vocabularies[word.lower()][0] >= min_to_count: # ignore the low frequency word
voc[word] = vocabularies[word]
file.close()
return voc
@staticmethod
def cal_chi_square(n11, n10, n01, n00):
return (n11 + n10 + n01 + n00) * (n11 * n00 - n10 * n01)**2 /\
((n11+n01) * (n11 + n10) * (n10 + n00) * (n01 + n00))
def get_class_word_count(self, x, y, voc=None):
"""
Count the word frequency in every classifications.
:param x: files to be count
:param y: classifications related to x
# :param vocabularies: features
:return: a set of Counters that counts the word frequency
"""
class_word_count = {}
for key in set(y):
class_word_count[key] = Counter() # init
for ii in range(len(x)):
file = open(x[ii], 'r', errors='ignore')
for line in file:
for word in r.split(line):
word = word.lower()
if not voc or word in voc:
class_word_count[y[ii]][word] += 1 # count
return class_word_count
def select_features(self, word_count, class_word_count, num):
"""Select features.
:param x: a list of files
:param y: the classification related to x
:return: a set of word to be features
"""
features = {}
total_word_count = {}
for cls in self.classes:
features[cls] = [(0, '')] * num
total_word_count[cls] = sum(class_word_count[cls].values())
for word in word_count:
for cls in self.classes:
n11 = class_word_count[cls][word]
n10 = word_count[word][0] - n11 # This word but not in classifier
n01 = total_word_count[cls] - n11 # Not this word but in classifier
n00 = 0
for c in self.classes:
if c != cls:
n00 += total_word_count[cls] - class_word_count[cls][word]
chi_s = Features.cal_chi_square(n11, n10, n01, n00)
if chi_s > features[cls][0][0]:
heappushpop(features[cls], (chi_s, word))
feature_set = {}
for cls in self.classes:
for c_s, _word in features[cls]:
# print(c_s, _word)
if _word:
feature_set[_word] = word_count[_word][1]
return feature_set
def read_file(self, name):
file = open(name, 'r', errors='ignore')
word_set = set()
for line in file:
for word in r.split(line):
word = word.lower()
if word in self.features:
word_set.add(word)
file.close()
return word_set
def get_x_vector(self, name, weight='tf'):
if weight not in self.weights:
print("Error: weight not found!")
return
file = open(name, 'r', errors='ignore')
word_array = self.cal_tf(file)
if weight == 'tfidf':
word_array = self.cal_tfidf(word_array)
file.close()
return word_array
def cal_tf(self, file):
word_array = [0] * len(self.features)
for line in file:
for word in r.split(line):
word = word.lower()
if word in self.features:
word_array[self.x_transform(word)] += 1
return word_array
def cal_tfidf(self, word_array):
for i in range(len(self.features)):
word_array[i] = 0 if not word_array[i] else \
(log2(word_array[i])+1)*log2(self.num_of_docs/self.features[self.x_le.inverse_transform(i)])
return word_array
def x_transform(self, thing):
return self.x_le.transform(thing)
def y_transform(self, thing):
return self.y_le.transform(thing)
