## 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.

### Getting ready

You have to have the `StatsBase`

package ready. This can be done by running `using StatsBase`

in the REPL.

### How to do it...

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 the following:

The

`countne()`

function does exactly the opposite of the`counteq()`

function in the preceding step. It returns the number of elements that are not equal in both the vectors:**countne(a,b)**The output would look like the following:

The...