Simple neural network code written in pure Octave/Matlab inspired by Andrew Ng's Machine Learning Course on Coursera.
The code for training a neural network is surprisingly concise, only a dozen lines of code or so (see nn_train.m and nn_predict.m).
To get octave on MacOS, use brew install octave.
To run the demos,
$ octave demo1.m
$ octave demo2.m