How do I solve the future warning -> % (min_groups, self.n_splits)), Warning) in python?

问题

When I run mean_acc() method in my program, there are % (min_groups, self.n_splits)), Warning) errors...

def mean_acc():
    models = [
        RandomForestClassifier(n_estimators=200, max_depth=3, random_state=0),
        LinearSVC(),
        MultinomialNB(),
        LogisticRegression(random_state=0)]
    CV = 6
    cv_df = pd.DataFrame(index=range(CV * len(models)))
    entries = []
    for model in models:
        model_name = model.__class__.__name__
        accuracies = cross_val_score(model, features, labels, scoring='accuracy', cv=CV)
        for fold_idx, accuracy in enumerate(accuracies):
            entries.append((model_name, fold_idx, accuracy))
    cv_df = pd.DataFrame(entries, columns=['model_name', 'fold_idx', 'accuracy'])

    print(cv_df.groupby('model_name').accuracy.mean())

These are the errors shown when I run my program with the mean_acc() method. May I know how do I solve these errors below? Please help to help me take a look at my codes above that have caused these errors, thanks!!!

 % (min_groups, self.n_splits)), Warning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\model_selection\_split.py:626: Warning: The least populated class in y has only 1 members, which is too few. The minimum number of members in any class cannot be less than n_splits=5.
  % (min_groups, self.n_splits)), Warning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\model_selection\_split.py:626: Warning: The least populated class in y has only 1 members, which is too few. The minimum number of members in any class cannot be less than n_splits=5.
  % (min_groups, self.n_splits)), Warning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\model_selection\_split.py:626: Warning: The least populated class in y has only 1 members, which is too few. The minimum number of members in any class cannot be less than n_splits=5.
  % (min_groups, self.n_splits)), Warning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\linear_model\logistic.py:432: FutureWarning: Default solver will be changed to 'lbfgs' in 0.22. Specify a solver to silence this warning.
  FutureWarning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\linear_model\logistic.py:459: FutureWarning: Default multi_class will be changed to 'auto' in 0.22. Specify the multi_class option to silence this warning.
  "this warning.", FutureWarning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\linear_model\logistic.py:432: FutureWarning: Default solver will be changed to 'lbfgs' in 0.22. Specify a solver to silence this warning.
  FutureWarning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\linear_model\logistic.py:459: FutureWarning: Default multi_class will be changed to 'auto' in 0.22. Specify the multi_class option to silence this warning.
  "this warning.", FutureWarning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\linear_model\logistic.py:432: FutureWarning: Default solver will be changed to 'lbfgs' in 0.22. Specify a solver to silence this warning.
  FutureWarning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\linear_model\logistic.py:459: FutureWarning: Default multi_class will be changed to 'auto' in 0.22. Specify the multi_class option to silence this warning.
  "this warning.", FutureWarning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\linear_model\logistic.py:432: FutureWarning: Default solver will be changed to 'lbfgs' in 0.22. Specify a solver to silence this warning.
  FutureWarning)
C:\Users\L31307\PycharmProjects\FYP\venv\lib\site-packages\sklearn\linear_model\logistic.py:459: FutureWarning: Default multi_class will be changed to 'auto' in 0.22. Specify the multi_class option to silence this warning.
  "this warning.", FutureWarning)

回答1:

If you want to ignore it, add the following to your code at the top:

import warnings
warnings.filterwarnings("ignore", category=FutureWarning)

Else specify solver as so:

LogisticRegression(solver='lbfgs')

Source:

solver : str, {‘newton-cg’, ‘lbfgs’, ‘liblinear’, ‘sag’, ‘saga’}, default: ‘liblinear’.
Algorithm to use in the optimization problem.

For small datasets, ‘liblinear’ is a good choice, whereas ‘sag’ and ‘saga’ are faster for large ones.
For multiclass problems, only ‘newton-cg’, ‘sag’, ‘saga’ and ‘lbfgs’ handle multinomial loss; ‘liblinear’ is limited to one-versus-rest schemes.
‘newton-cg’, ‘lbfgs’ and ‘sag’ only handle L2 penalty, whereas ‘liblinear’ and ‘saga’ handle L1 penalty.

回答2:

If you are using Logistic Regression Model having penalty='l1' as hyper-parameter you can use solver='liblinear'

My Code sample::

logistic_regression_model=LogisticRegression(penalty='l1',dual=False,max_iter=110, solver='liblinear')

来源：https://stackoverflow.com/questions/52640386/how-do-i-solve-the-future-warning-min-groups-self-n-splits-warning-in

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python

scikit-learn

linearmodels

future-warning