Neural Networks – A Multilayer Perceptron in Matlab

Previously, Matlab Geeks discussed a simple perceptron, which involves feed-forward learning based on two layers: inputs and outputs. Today we’re going to add a little more complexity by including a third layer, or a hidden layer into the network. A reason for doing so is based on the concept of linear separability. While logic gates like “OR”, “AND” or “NAND” can have 0’s and 1’s separated by a single line (or hyperplane in multiple dimensions), this linear separation is not possible for “XOR” (exclusive OR).

Linear separability for OR and XOR logic gates

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Neural Networks – A perceptron in Matlab

Neural networks can be used to determine relationships and patterns between inputs and outputs. A simple single layer feed forward neural network which has a to ability to learn and differentiate data sets is known as a perceptron.

Single layer feed forward perceptron

By iteratively “learning” the weights, it is possible for the perceptron to find a solution to linearly separable data (data that can be separated by a hyperplane). In this example, we will run a simple perceptron to determine the solution to a 2-input OR.
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