Real-world data sets can be messy, incomplete, and in a variety of formats. You may have simple numeric data. But sometimes you’re combining several different data types, such as sensor signals, text, and streaming images from a camera.

Choosing the right model is a balancing act. Highly flexible models tend to overfit data by modeling minor variations that could be noise. On the other hand, simple models may assume too much. There are always tradeoffs between model speed, accuracy, and complexity.