sams-neurons/sam-neurons.js

class NeuralNetwork {
    constructor(inputNodes, hiddenNodes, outputNodes) {
        this.inputNodes = inputNodes;
        this.hiddenNodes = hiddenNodes;
        this.outputNodes = outputNodes;

        // Initialize weights with random values between -1 and 1
        this.weights_ih = this.initializeWeights(this.hiddenNodes, this.inputNodes);
        this.weights_ho = this.initializeWeights(this.outputNodes, this.hiddenNodes);

        // Biases
        this.bias_h = this.initializeBiases(this.hiddenNodes);
        this.bias_o = this.initializeBiases(this.outputNodes);

        // Learning rate
        this.learningRate = 0.1;
    }

    // Helper method to initialize weights
    initializeWeights(rows, cols) {
        return Array(rows).fill().map(() => Array(cols).fill().map(() => Math.random() * 2 - 1));
    }

    // Helper method to initialize biases
    initializeBiases(size) {
        return Array(size).fill().map(() => Math.random() * 2 - 1);
    }

    // Sigmoid activation function
    sigmoid(x) {
        return 1 / (1 + Math.exp(-x));
    }

    // Sigmoid derivative (used for backpropagation)
    sigmoidDerivative(x) {
        return x * (1 - x);
    }

    // Feedforward function
    feedforward(inputArray) {
        // Calculate hidden layer outputs
        let hidden = this.weights_ih.map((row, i) => 
            this.sigmoid(row.reduce((sum, weight, j) => sum + weight * inputArray[j], 0) + this.bias_h[i])
        );

        // Calculate output layer outputs
        let output = this.weights_ho.map((row, i) => 
            this.sigmoid(row.reduce((sum, weight, j) => sum + weight * hidden[j], 0) + this.bias_o[i])
        );

        return output;
    }

    // Train the network
    train(inputArray, targetArray) {
        // Feedforward
        let hidden = this.weights_ih.map((row, i) => 
            this.sigmoid(row.reduce((sum, weight, j) => sum + weight * inputArray[j], 0) + this.bias_h[i])
        );
        let outputs = this.weights_ho.map((row, i) => 
            this.sigmoid(row.reduce((sum, weight, j) => sum + weight * hidden[j], 0) + this.bias_o[i])
        );

        // Calculate the output errors
        let outputErrors = targetArray.map((target, i) => target - outputs[i]);

        // Calculate output gradients
        let outputGradients = outputs.map((output, i) => 
            this.sigmoidDerivative(output) * outputErrors[i] * this.learningRate
        );

        // Calculate hidden errors
        let hiddenErrors = this.weights_ho[0].map((_, i) => 
            this.weights_ho.reduce((sum, row) => sum + row[i] * outputErrors[0], 0)
        );

        // Calculate hidden gradients
        let hiddenGradients = hidden.map((h, i) => 
            this.sigmoidDerivative(h) * hiddenErrors[i] * this.learningRate
        );

        // Update weights and biases
        this.weights_ho = this.weights_ho.map((row, i) => 
            row.map((weight, j) => weight + outputGradients[i] * hidden[j])
        );
        this.weights_ih = this.weights_ih.map((row, i) => 
            row.map((weight, j) => weight + hiddenGradients[i] * inputArray[j])
        );
        this.bias_o = this.bias_o.map((bias, i) => bias + outputGradients[i]);
        this.bias_h = this.bias_h.map((bias, i) => bias + hiddenGradients[i]);
    }
}

// Example usage:
let nn = new NeuralNetwork(2, 4, 1);  // Increased hidden nodes to 4

// Example dataset (XOR problem)
let inputs = [
    [0, 0],
    [0, 1],
    [1, 0],
    [1, 1]
];
let targets = [
    [0],
    [1],
    [1],
    [0]
];

// Training the neural network
for (let i = 0; i < 50000; i++) {  // Increased training iterations
    let index = Math.floor(Math.random() * 4);
    nn.train(inputs[index], targets[index]);
}

// Testing the neural network
console.log(nn.feedforward([0, 0]));
console.log(nn.feedforward([0, 1]));
console.log(nn.feedforward([1, 0]));
console.log(nn.feedforward([1, 1]));