How to get probabilities values with keras?

Question

tensorflow version = '1.12.0'

keras version = '2.1.6-tf'

I'm using keras with tensorflow backend.

I want to get the probabilities values of the prediction. I want the probabilities to sum up to 1. I tried using 'softmax' and 'categorical_crossentropy' but nothing works.

This is my model:

X = pickle.load(open("X.pickle", "rb"))
y = pickle.load(open("y.pickle", "rb"))

number_of_gestures = 5 
y = to_categorical(y, num_classes=number_of_gestures) #to_categorical is a function from keras - np_utils.

model = Sequential()
model.add(Conv2D(16, (2,2), input_shape=(IMG_SIZE, IMG_SIZE, 1), activation='relu'))

model.add(MaxPooling2D(pool_size=(2, 2), strides=(2, 2), padding='same'))

model.add(Conv2D(32, (5,5), activation='relu'))

model.add(MaxPooling2D(pool_size=(5, 5), strides=(5, 5), padding='same'))

model.add(Conv2D(64, (5,5), activation='relu'))

model.add(Flatten())

model.add(Dense(128, activation='relu'))

model.add(Dropout(0.2))

model.add(Dense(number_of_gestures, activation='softmax'))

sgd = optimizers.SGD(lr=1e-2)
model.compile(loss='categorical_crossentropy', optimizer=sgd, metrics=['accuracy'])
model.fit(X, y, batch_size=500, epochs=40, validation_split=0.1)

The probabilities looks like that:

[1. 0. 0. 0. 0.]

And I want it to look like this:

[0.897. 0.023. 0.158. 0.780. 0.1021]

I know it does not sum up to 1 but this is just an example.

Answer 1

I faced such a problem using CNN in Keras. Even, I thought that the output is being processed in the such a way like the argmax().

• But, after investigating the model, I found that the model are learned and generalised so well that the labels got binarized ( 0s and 1s ). Remember, that we give the label of an image as a one hot vector ( like [ 1 0 0 0 ] ). The NN learned it so well that the output, usually being a probability vector , was now a one hot vector on which it was trained.

• Another way to prove this is that you are using a softmax activation function at the output layer. A softmax function produces probabilities which sum up to 1. The sum of all class probabilities is 1. In the vector [ 1 0 0 0 0 ]. The sum of all numbers is 1. Hence the output is valid.

This is just a different phase in training your model. You can try to increase the size of your dataset or lower the learning rate to 0.0001 or even smaller.

Answer 2

My guess is that you are calling predict when you need to call predict_proba.

Answer 3

As I found on stackoverflow something similar that did the job for me, here is the link [StackOverflow Link][1]. Which I'm citing "

I think I found the mistake. You are rescaling your train and test data with the ImageDataGenerator. But you are not doing that when testing a single image. Try this:

    #Making new Predictions
    import numpy as np
    from keras.preprocessing import image
    
    test_image_luna=image.load_img('dataset/single/SkilletLuna.JPG',target_size=(64,64))
    test_image2=image.img_to_array(test_image_luna)/255 #add this one
    test_image2=np.expand_dims(test_image2,axis=0)
    luna=classifier.predict_proba(test_image2)


  [1]: https://stackoverflow.com/questions/54513742/how-do-i-get-probability-confidence-as-output-for-a-cnn-using-keras-in-python

Answer 4

To get probabilities, you have to use something like this:

probabilities = tf.nn.softmax(prediction_results).numpy()