Anomaly Detection

What is an Anomaly

An Anomaly defined as:

Something that is different from what is usual or expected.

Detecting anomalies has many useful applications. For example anomaly detection enables us to detect cancer in MRI images, detecting credit card fraud, pricing glitches and much more.

Can you find the anomaly in the picture below?

So as you probably guessed, the red fish is the anomaly. It is different from the rest because it deviates from the established normal pattern of blue fish.

Let’s take another example. Using the last technique we would assume that the anomaly is the green car in the picture below since the rest of the vehicles are red.

However, you could also say the motorcycle is an anomaly if you were only familiar with seeing cars and trucks. This illustrates that we need to be able to define what an anomaly is for us.

Once we establish what is the norm it is easy to define what the anomaly is. We simply ask if the observation, which is this case is a particular vehicle, fits the normal pattern.