给出这个简单的多标签分类示例(取自这个问题,use scikit-learn to classify into multiple categories)
import numpy as np
from sklearn.pipeline import Pipeline
from sklearn.feature_extraction.text import CountVectorizer
from sklearn.svm import LinearSVC
from sklearn.feature_extraction.text import TfidfTransformer
from sklearn.multiclass import OneVsRestClassifier
from sklearn import preprocessing
from sklearn.metrics import accuracy_score
X_train = np.array(["new york is a hell of a town",
"new york was originally dutch",
"the big apple is great",
"new york is also called the big apple",
"nyc is nice",
"people abbreviate new york city as nyc",
"the capital of great britain is london",
"london is in the uk",
"london is in england",
"london is in great britain",
"it rains a lot in london",
"london hosts the british museum",
"new york is great and so is london",
"i like london better than new york"])
y_train_text = [["new york"],["new york"],["new york"],["new york"], ["new york"],
["new york"],["london"],["london"],["london"],["london"],
["london"],["london"],["new york","london"],["new york","london"]]
X_test = np.array(['nice day in nyc',
'welcome to london',
'london is rainy',
'it is raining in britian',
'it is raining in britian and the big apple',
'it is raining in britian and nyc',
'hello welcome to new york. enjoy it here and london too'])
y_test_text = [["new york"],["london"],["london"],["london"],["new york", "london"],["new york", "london"],["new york", "london"]]
lb = preprocessing.MultiLabelBinarizer()
Y = lb.fit_transform(y_train_text)
Y_test = lb.fit_transform(y_test_text)
classifier = Pipeline([
('vectorizer', CountVectorizer()),
('tfidf', TfidfTransformer()),
('clf', OneVsRestClassifier(LinearSVC()))])
classifier.fit(X_train, Y)
predicted = classifier.predict(X_test)
print "Accuracy Score: ",accuracy_score(Y_test, predicted)代码运行良好,并打印准确度分数,但是如果我将y_test_text更改为
y_test_text = [["new york"],["london"],["england"],["london"],["new york", "london"],["new york", "london"],["new york", "london"]]我得到了
Traceback (most recent call last):
File "/Users/scottstewart/Documents/scikittest/example.py", line 52, in <module>
print "Accuracy Score: ",accuracy_score(Y_test, predicted)
File "/Library/Python/2.7/site-packages/sklearn/metrics/classification.py", line 181, in accuracy_score
differing_labels = count_nonzero(y_true - y_pred, axis=1)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/scipy/sparse/compressed.py", line 393, in __sub__
raise ValueError("inconsistent shapes")
ValueError: inconsistent shapes注意引入了'england‘标签,该标签不在训练集中。我如何使用多标签分类,以便在引入“测试”标签时,我仍然可以运行一些指标?或者这有可能吗?
编辑:感谢大家的回答,我想我的问题更多的是关于scikit二进制化器是如何工作的,或者应该如何工作。对于我简短的示例代码,如果我将y_test_text更改为
y_test_text = [["new york"],["new york"],["new york"],["new york"],["new york"],["new york"],["new york"]]它可以工作--我的意思是我们已经适应了这个标签,但在这种情况下,我得到了
ValueError: Can't handle mix of binary and multilabel-indicator发布于 2018-05-15 22:03:56
正如在另一条评论中提到的,就我个人而言,我希望二进制化器在“转换”时忽略看不到的类。如果测试样本呈现的特征与训练中使用的特征不同,则消耗二值化器结果的分类器可能反应不佳。
我只是解决了这个问题,只是从样本中删除了不可见的类。我认为这是一种比动态更改合适的二进制代码或(另一种选择)扩展它以允许忽略的方法更安全的方法。
list(map(lambda names: np.intersect1d(lb.classes_, names), y_test_text))没有运行你的实际代码
https://stackoverflow.com/questions/31503874
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