Implement Neural Network Classifier with Matlab

Neural Network classifier is a multilayer network of logistic units, with each unit takes some inputs and produces one output using a logistic classifier and output of one unit can be the input of another. The following schematic represents a neural network with one hidden layer.  Similar to Linear Regression classifier, squared error loss will be used. Below is the forward propagation algorithm to compute the activation “act", where W1/W2 represent weights of each edge, b1/b2 represent biases.  According to the back propagation algorithm, the cost function and gradients could be calculated as follows.