In [1]:
%%html
<style>
@import url('https://fonts.googleapis.com/css?family=Orbitron|Roboto');
body {background-color: #add8e6;}
a {color: darkblue; font-family: 'Roboto';}
h1 {color: steelblue; font-family: 'Orbitron'; text-shadow: 4px 4px 4px #aaa;}
h2, h3 {color: #483d8b; font-family: 'Orbitron'; text-shadow: 4px 4px 4px #aaa;}
h4 {color: slategray; font-family: 'Roboto';}
span {text-shadow: 4px 4px 4px #ccc;}
div.output_prompt, div.output_area pre {color: #483d8b;}
div.input_prompt, div.output_subarea {color: darkblue;}
div.output_stderr pre {background-color: #add8e6;}
div.output_stderr {background-color: #483d8b;}
</style>
In [3]:
from keras.datasets import mnist
# use Keras to import pre-shuffled MNIST database
(X_train, y_train), (X_test, y_test) = mnist.load_data()
print("The MNIST database has a training set of %d examples." % len(X_train))
print("The MNIST database has a test set of %d examples." % len(X_test))
2. Visualize the First Six Training Images¶
In [4]:
import matplotlib.pyplot as plt
%matplotlib inline
import matplotlib.cm as cm
import numpy as np
# plot first six training images
fig = plt.figure(figsize=(20,20))
for i in range(6):
ax = fig.add_subplot(1, 6, i+1, xticks=[], yticks=[])
ax.imshow(X_train[i], cmap='bone')
ax.set_title(str(y_train[i]))
3. View an Image in More Detail¶
In [5]:
def visualize_input(img, ax):
ax.imshow(img, cmap='gray')
width, height = img.shape
thresh = img.max()/2.5
for x in range(width):
for y in range(height):
ax.annotate(str(round(img[x][y],2)), xy=(y,x),
horizontalalignment='center',
verticalalignment='center',
color='white' if img[x][y]<thresh else 'black')
fig = plt.figure(figsize = (12,12))
ax = fig.add_subplot(111)
visualize_input(X_train[0], ax)
4. Rescale the Images by Dividing Every Pixel in Every Image by 255¶
In [6]:
# rescale [0,255] --> [0,1]
X_train = X_train.astype('float32')/255
X_test = X_test.astype('float32')/255
5. Encode Categorical Integer Labels Using a One-Hot Scheme¶
In [7]:
from keras.utils import np_utils
# print first ten (integer-valued) training labels
print('Integer-valued labels:')
print(y_train[:10])
# one-hot encode the labels
y_train = np_utils.to_categorical(y_train, 10)
y_test = np_utils.to_categorical(y_test, 10)
# print first ten (one-hot) training labels
print('One-hot labels:')
print(y_train[:10])
6. Define the Model Architecture¶
In [14]:
from keras.models import Sequential
from keras.layers import Dense, Dropout, Flatten
# define the model
model = Sequential()
model.add(Flatten(input_shape=X_train.shape[1:]))
model.add(Dense(512, activation='relu'))
model.add(Dropout(0.2))
model.add(Dense(512, activation='relu'))
model.add(Dropout(0.2))
model.add(Dense(10, activation='softmax'))
# summarize the model
model.summary()
7. Compile the Model¶
In [15]:
# compile the model
model.compile(loss='categorical_crossentropy',
optimizer='nadam',
metrics=['accuracy'])
8. Calculate the Classification Accuracy on the Test Set (Before Training)¶
In [16]:
# evaluate test accuracy
score = model.evaluate(X_test, y_test, verbose=0)
accuracy = 100*score[1]
# print test accuracy
print('Test accuracy: %.4f%%' % accuracy)
9. Train the Model¶
In [17]:
from keras.callbacks import ModelCheckpoint
# train the model
checkpointer = ModelCheckpoint(filepath='mnist.model.best.hdf5',
verbose=1, save_best_only=True)
hist = model.fit(X_train, y_train, batch_size=128, epochs=10,
validation_split=0.2, callbacks=[checkpointer],
verbose=1, shuffle=True)
10. Load the Model with the Best Classification Accuracy on the Validation Set¶
In [18]:
# load the weights that yielded the best validation accuracy
model.load_weights('mnist.model.best.hdf5')
11. Calculate the Classification Accuracy on the Test Set¶
In [19]:
# evaluate test accuracy
score = model.evaluate(X_test, y_test, verbose=0)
accuracy = 100*score[1]
# print test accuracy
print('Test accuracy: %.4f%%' % accuracy)