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# Deviation metrics

Metrics that help calculate the distance or similarity between two vectors are called deviation metrics. These metrics help us understand the relationship between the different vectors and the data in them.

You have to have the `StatsBase` package ready. This can be done by running `using StatsBase` in the REPL.

## How to do it...

1. For getting the number of elements in a vector that are exactly equal to a set of elements in a vector, we can use the `counteq()` function.

For example, consider the two vectors: a = [1, 2, 3, 4, 5, 6] and b = [4, 2, 3, 5, 6, 7].

The elements at the second and third indexes are equal to each other, so they will be returned as a result of the `counteq()` function:

```counteq(a,b)
```

The output would look like ...

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