[英]NLTK Classifier giving only negative as answer in Sentiment Analysis
我正在使用 NLTK 進行情緒分析,使用內置的語料庫movie_reviews
進行訓練,並且每次我都得到neg
結果。
我的代碼:
import nltk
import random
import pickle
from nltk.corpus import movie_reviews
from os.path import exists
from nltk.classify import apply_features
from nltk.tokenize import word_tokenize, sent_tokenize
documents = [(list(movie_reviews.words(fileid)), category)
for category in movie_reviews.categories()
for fileid in movie_reviews.fileids(category)]
all_words = []
for w in movie_reviews.words():
all_words.append(w.lower())
all_words = nltk.FreqDist(all_words)
word_features = list(all_words.keys())
print(word_features)
def find_features(document):
words = set(document)
features = {}
for w in word_features:
features[w] = (w in words)
return features
featuresets = [(find_features(rev), category) for (rev, category) in documents]
numtrain = int(len(documents) * 90 / 100)
training_set = apply_features(find_features, documents[:numtrain])
testing_set = apply_features(find_features, documents[numtrain:])
classifier = nltk.NaiveBayesClassifier.train(training_set)
classifier.show_most_informative_features(15)
Example_Text = " avoids annual conveys vocal thematic doubts fascination slip avoids outstanding thematic astounding seamless"
doc = word_tokenize(Example_Text.lower())
featurized_doc = {i:(i in doc) for i in word_features}
tagged_label = classifier.classify(featurized_doc)
print(tagged_label)
在這里,我用NaiveBayes Classifier
在那里我與訓練數據movie_reviews
語料庫,然后用這個訓練分類來測試我的情緒Example_test
。
現在你可以看到我的Example_Text
,它有一些隨機的詞。 當我做classifier.show_most_informative_features(15)
,它給了我一個包含 15 個單詞的列表,這些單詞的正負比例最高。 我選擇了此列表中顯示的正面詞。
Most Informative Features
avoids = True pos : neg = 12.1 : 1.0
insulting = True neg : pos = 10.8 : 1.0
atrocious = True neg : pos = 10.6 : 1.0
outstanding = True pos : neg = 10.2 : 1.0
seamless = True pos : neg = 10.1 : 1.0
thematic = True pos : neg = 10.1 : 1.0
astounding = True pos : neg = 10.1 : 1.0
3000 = True neg : pos = 9.9 : 1.0
hudson = True neg : pos = 9.9 : 1.0
ludicrous = True neg : pos = 9.8 : 1.0
dread = True pos : neg = 9.5 : 1.0
vocal = True pos : neg = 9.5 : 1.0
conveys = True pos : neg = 9.5 : 1.0
annual = True pos : neg = 9.5 : 1.0
slip = True pos : neg = 9.5 : 1.0
那么為什么我沒有得到pos
作為結果,為什么即使分類器經過正確訓練,我總是得到neg
?
問題在於您將所有單詞都包含為特征,而“word:False”形式的特征會產生大量額外的噪音,從而淹沒了這些積極特征。 我查看了兩個對數概率,它們非常相似:-812 與 -808。 在這類問題中,一般只使用 word:True 風格特征是合適的,因為所有其他的只會增加噪音。
我復制了你的代碼,但修改了最后三行如下:
featurized_doc = {c:True for c in Example_Text.split()}
tagged_label = classifier.classify(featurized_doc)
print(tagged_label)
並得到輸出“pos”
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.