How to find Top features from Naive Bayes using sklearn pipeline - scikit-learn

Question

How to find Top features from Naive Bayes using sklearn pipeline
Hi all,
I am trying to apply Naive Bayes(MultinomialNB ) using pipelines and i came up with the code. However I am interested in finding top 10 positve and negative words , but not able to succeed. when I searched , I got the code for finding top features which i mentioned below. However when i tried using the code using pipeline i am getting the error which i mentioned below. I tried searching exhaustively , but got the code without using pipeline.But when i use the code with my output from pipeline, it is not working. COuld you please help me on how to find feature importance from pipeline output.
# Pipeline dictionary
pipelines = {
'bow_MultinomialNB' : make_pipeline(
CountVectorizer(),
preprocessing.Normalizer(),
MultinomialNB()
)
}
# List tuneable hyperparameters of our pipeline
pipelines['bow_MultinomialNB'].get_params()
# BOW - MultinomialNB hyperparameters
bow_MultinomialNB_hyperparameters = {
'multinomialnb__alpha' : [1000,500,100,50,10,5,1,0.5,0.1,0.05,0.01,0.005,0.001,0.0005,0.0001]
}
# Create hyperparameters dictionary
hyperparameters = {
'bow_MultinomialNB' : bow_MultinomialNB_hyperparameters
}
tscv = TimeSeriesSplit(n_splits=3) #For time based splitting
for name, pipeline in pipelines.items():
print("NAME:",name)
print("PIPELINE:",pipeline)
%time
# Create empty dictionary called fitted_models
fitted_models = {}
# Loop through model pipelines, tuning each one and saving it to fitted_models
for name, pipeline in pipelines.items():
# Create cross-validation object from pipeline and hyperparameters
model = GridSearchCV(pipeline, hyperparameters[name], cv=tscv, n_jobs=1,verbose=1)
# Fit model on X_train, y_train
model.fit(X_train, y_train)
# Store model in fitted_models[name]
fitted_models[name] = model
# Print '{name} has been fitted'
print(name, 'has been fitted.')
FEAURE IMPORTANCE:-
pipelines['bow_MultinomialNB'].steps[2][1].classes__
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-125-7d45b007e86b> in <module>()
----> 1 pipelines['bow_MultinomialNB'].steps[2][1].classes_
AttributeError: 'MultinomialNB' object has no attribute 'classes_'
pipelines['bow_MultinomialNB'].steps[0][1].get_feature_names()
---------------------------------------------------------------------------
NotFittedError Traceback (most recent call last)
<ipython-input-126-2883929221d1> in <module>()
----> 1 pipelines['bow_MultinomialNB'].steps[0][1].get_feature_names()
~\Anaconda3\lib\site-packages\sklearn\feature_extraction\text.py in get_feature_names(self)
958 def get_feature_names(self):
959 """Array mapping from feature integer indices to feature name"""
--> 960 self._check_vocabulary()
961
962 return [t for t, i in sorted(six.iteritems(self.vocabulary_),
~\Anaconda3\lib\site-packages\sklearn\feature_extraction\text.py in _check_vocabulary(self)
301 """Check if vocabulary is empty or missing (not fit-ed)"""
302 msg = "%(name)s - Vocabulary wasn't fitted."
--> 303 check_is_fitted(self, 'vocabulary_', msg=msg),
304
305 if len(self.vocabulary_) == 0:
~\Anaconda3\lib\site-packages\sklearn\utils\validation.py in check_is_fitted(estimator, attributes, msg, all_or_any)
766
767 if not all_or_any([hasattr(estimator, attr) for attr in attributes]):
--> 768 raise NotFittedError(msg % {'name': type(estimator).__name__})
769
770
NotFittedError: CountVectorizer - Vocabulary wasn't fitted.
x=pipelines['bow_MultinomialNB'].steps[0][1]._validate_vocabulary()
x.get_feature_names()
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-120-f620c754a34e> in <module>()
----> 1 x.get_feature_names()
AttributeError: 'NoneType' object has no attribute 'get_feature_names'
Regards,
Shree