What makes aGood Features? Machine Learning Recipes.

Classifier are only as goof as the features you provide. that means coming up with good features, is one of the most important jobs in machine learning.

But what makes a good feature and how can you tell ?

If you are doing binary classification , then a good feature makes it easy to decide between things.

ex- imagine we wanted to write a classifier to tell the difference between two dogs , greyhounds and labradors

here we will use two features , the dogs height in inches and there eye color
just for this toy example , lets make couple assumptions about dogs to keep things simple

First - greyhounds usually taller than  labradors , next we will pretend that dogs have only two eye colors - blue and brown and we will say the color of eyes does not depends on breed of dog, this mean that one of these features is usefull and other tells us nothing.