Congratulations! You just learned two important things, of which the most important is that, as a typical machine learning operator, you will spend most of your time understanding and refining the data—exactly what we just did in our first, tiny machine learning example. We hope that this example helped you to start switching your mental focus from algorithms to data.

Then, you learned how important it is to have the correct experiment setup, and that it is vital to not mix up training and testing. Admittedly, the use of polynomial fitting is not the coolest thing in the machine learning world; we chose it so that you would not be distracted by the coolness of some shiny algorithm when we conveyed those two most important messages we mentioned earlier.

So, let's move on to Chapter 2, Classifying with Real-world Examples, we are on the topic of classification. Now, we will apply the concepts on a very specific, but very important, type of data, namely text.