This post covers how to build a simple neural network from scratch that can recognize handwritten digits from the MNIST dataset.
The MNIST dataset contains 60,000 training images and 10,000 test images of handwritten digits (0–9).
Each image is flattened into a 784-dimensional vector, which enables us to input directly into our neural network, which has 784 input neurons.
Our neural network has three layers: an input layer (784 neurons), a hidden layer (10 neurons with ReLU activation), and an output layer (10 neurons with softmax activation).
The learning process of a neural network involves forward propagation, activation functions, backward propagation, and gradient descent.
ReLU is an activation function used to introduce non-linearity. It is defined as: ReLU outputs the input ZZ if it is positive, and zero otherwise.
Softmax is an activation function applied to the output layer to interpret the model’s predictions as probabilities.
Backward propagation calculates how much each weight and bias contributed to the error in the model’s predictions.
After calculating the gradients, we use gradient descent to update the parameters, moving in the direction that reduces the network’s error.
This post demonstrated how to build a simple neural network from scratch in Python to classify MNIST handwritten digits.