[英]Feature Importance extraction of Decision Trees (scikit-learn)
我一直試圖掌握我建模的決策樹中使用的特征的重要性。 我有興趣發現在節點處選擇的每個特征的權重以及術語本身。 我的數據是一堆文件。 這是我的決策樹代碼,我修改了 scikit-learn 中提取的代碼片段( http://scikit-learn.org/stable/auto_examples/ensemble/plot_forest_importances.html ):
from sklearn.feature_extraction.text import TfidfVectorizer
### Feature extraction
tfidf_vectorizer = TfidfVectorizer(stop_words=stopwords,
use_idf=True, tokenizer=None, ngram_range=(1,2))#ngram_range=(1,0)
tfidf_matrix = tfidf_vectorizer.fit_transform(data[:, 1])
terms = tfidf_vectorizer.get_features_names()
### Define Decision Tree and fit
dtclf = DecisionTreeClassifier(random_state=1234)
dt = data.copy()
y = dt["label"]
X = tfidf_matrix
fitdt = dtclf.fit(X, y)
from sklearn.datasets import load_iris
from sklearn import tree
### Visualize Devision Tree
with open('data.dot', 'w') as file:
tree.export_graphviz(dtclf, out_file = file, feature_names = terms)
file.close()
import subprocess
subprocess.call(['dot', '-Tpdf', 'data.dot', '-o' 'data.pdf'])
### Extract feature importance
importances = dtclf.feature_importances_
indices = np.argsort(importances)[::-1]
# Print the feature ranking
print('Feature Ranking:')
for f in range(tfidf_matrix.shape[1]):
if importances[indices[f]] > 0:
print("%d. feature %d (%f)" % (f + 1, indices[f], importances[indices[f]]))
print ("feature name: ", terms[indices[f]])
fitdt = dtclf.fit(X, y)
with open(...):
tree.export_graphviz(dtclf, out_file = file, feature_names = terms)
提前致謝
對於您的第一個問題,您需要使用terms = tfidf_vectorizer.get_feature_names()
從矢量化器中獲取特征名稱。 對於第二個問題,您可以使用feature_names = terms
調用export_graphviz
以獲取變量的實際名稱以顯示在可視化中(查看export_graphviz
的完整文檔,了解可能對改進可視化有用的許多其他選項。
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