Beginning Anomaly Detection Using

unsupervised anomaly detection.

 Mutant  Fish

To better understand what an isolation forest does, let’s look at an imaginary scenario. 

At a particularly large lake, an irresponsible fish breeder has released a mutant species 

of fish that looks eerily similar to the native species, but are on average bigger than the 

native species. Additionally, the proportion of the length of its tail fin to the length of its 

body is larger than the native species. All in all, there are three features you can use to 

distinguish the invasive, mutant species from the native species.

Here’s a visual example detailing the differences of an average specimen of both 

species. You can see the 

native species in Figure 

2-7

.

Figure 2-7.  This is an example of the native species at this lake

Chapter 2   traditional Methods of anoMaly deteCtion

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You can see the