I was trying to create a sample file for training a neural network and ran into a common problem: the feature values are all over the place. In this example I’m working with demographical real-world values for countries. For example, a feature for GDP per person in a country ranges from 551.27 to 88286.0, whereas estimates for corruption range between -1.56 to 2.42. This can be very confusing for machine learning algorithms, as they can end up treating bigger values as more important signals.
To handle this issue, we want to scale all the feature values into roughly the same range. We can do this by taking each feature value, subtracting its mean (thereby shifting the mean to 0), and dividing by the standard deviation (normalising the distribution). This is a piece of code I’ve implemented a number of times for various projects, so it’s time to write a nice reusable script. Hopefully it can be helpful for others as well. I chose to do this in python, as it’s easies to run compared to C++ and Java (doesn’t need to be compiled), but has better support for real-valued numbers compared to bash scripting.