A convolutional layer example with Keras to recognize digits

In the third chapter, we introduced a simple neural network to classify digits using Keras and we got 94%. In this chapter, we will work to improve that value above 99% using convolutional networks. Actual values may vary slightly due to variability in initialization.

First of all, we can start by improving the neural network we had defined by using 400 hidden neurons and run it for 30 epochs; that should get us already up to around 96.5% accuracy:

    hidden_neurons = 400
    epochs = 30

Next we could try scaling the input. Images are comprised of pixels, and each pixel has an integer value between 0 and 255. We could make that value a float and scale it between 0 and 1 by adding these four lines of code right after we define our input:

X_train = X_train.astype('float32')     
X_test = X_test.astype('float32')     
X_train /= 255     
X_test /= 255

If we run our network now, we get a poorer accuracy, just above 92%, but we need not...