Comparison of Deepnet & Neuralnet

Based on two R packages for neural networks. In this article, I compare two available R packages for using neural networks to model data: neuralnet and deepnet. Through the comparisons I highlight various challenges in finding good hyperparameter values. I show that some needed hyperparameters differ when using these two packages, even with the same underlying algorithmic approach. Both packages can be obtained via the R CRAN repository (see links at the end). I will focus on a simple time series example, composed of two predictors and the performance of the packages to predict future data after being trained on past data using a simple 5-neuron network. Note that most of what you read about in deep learning with neural networks are "classification" problems (more later); nonetheless such networks have promise for predicting continuous data including time series. Briefly, a neural network (also called a multilayer-perceptron etc.) is a connected network of neurons as shown here. An example neural network (generated using neuralnet). Note that except for the input layer (where the predictor values are fed in), the inputs to a neuron have weights specific to that neuron, so the output of a neuron is "re-used" as input to all neurons in the next layer, with unique weights. Before moving on to a brief description of how neural networks compute predictions, it is worth reflecting on the number of independent parameters in neural network models as compared to, for example, linear regression.