Why does predict_proba function print the probabilities in reverse order?

Question

I am using scikit-learn to implement classification using Logistic Regression.
The class labels are predicted using predict() function, while the predicted probabilities are printed using predict_proba() function.

The code snippet is pasted below:

# Partition the dataset into train and test data
X_train, X_test, y_train, y_test = train_test_split(ds_X, ds_y, test_size=0.33, random_state=42) 

y_pred = logreg.predict(X_test)                             # Predicted class labels from test features
y_predicted_proba = logreg.predict_proba(X_test)            # Predicted probabilities from test features

The predicted labels are printed as

array([1, 1, 1, 1, 1, 1, 1, 1, 0, 1.......... and so on

The corresponding predicted probabilities are printed as

array([[ 0.03667012,  0.96332988],
       [ 0.03638475,  0.96361525],
       [ 0.03809274,  0.96190726],
       [ 0.01746768,  0.98253232],
       [ 0.02742639,  0.97257361],
       [ 0.03676579,  0.96323421],
       [ 0.02881874,  0.97118126],
       [ 0.03082288,  0.96917712],
       [ 0.65332179,  0.34667821],
       [ 0.02091977,  0.97908023],
                   .
                   '
       and so on

Observe,
the first predicted label – 1
the first predicted probability – [ 0.03667012, 0.96332988]

Why is 0.03667012 printed first, instead of 0.96332988 ?
Should it have been the other way?

Asked By: User456898

||

Source

Answer 1

The column 0 is the probability for class 0,

and the column 1 is the probability for the class 1.

If you have n classes the output probabilities shape will be (n_examples, n_classes).

Answered By: A. Attia

Answer 2

You can use:
logreg.classes_ to resolve what element in your probability array corresponds to which class. In your case its [False,True]

Answered By: Michael Higgins

Why does predict_proba function print the probabilities in reverse order?

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