3.1 Display the test set and predictions

# set up the figure
fig = plt.figure(figsize=(15, 7))
fig.subplots_adjust(left=0, right=1, bottom=0, top=1, hspace=0.05, wspace=0.05)

# plot the digits: each image is 8x8 pixels
for i in range(120):
    ax = fig.add_subplot(6, 20, i + 1, xticks=[], yticks=[])
    ax.imshow(X_test[i,:].reshape((8,8)),
              cmap=plt.cm.gray_r, 
              interpolation='nearest')
    
    # label the image with the target value
    ax.text(0, 7, str(prediction_values[i]))