

# Standard Scaler

> 译者：[flink.sojb.cn](https://flink.sojb.cn/)


## Description

The standard scaler scales the given data set, so that all features will have a user specified mean and variance. In case the user does not provide a specific mean and standard deviation, the standard scaler transforms the features of the input data set to have mean equal to 0 and standard deviation equal to 1. Given a set of input data $x_1, x_2,… x_n$, with mean:

and standard deviation:

The scaled data set $z_1, z_2,…,z_n$ will be:

where $\textit{std}$ and $\textit{mean}$ are the user specified values for the standard deviation and mean.

## Operations

`StandardScaler` is a `Transformer`. As such, it supports the `fit` and `transform` operation.

### Fit

StandardScaler is trained on all subtypes of `Vector` or `LabeledVector`:

*   `fit[T &lt;: Vector]: DataSet[T] =&gt; Unit`
*   `fit: DataSet[LabeledVector] =&gt; Unit`

### Transform

StandardScaler transforms all subtypes of `Vector` or `LabeledVector` into the respective type:

*   `transform[T &lt;: Vector]: DataSet[T] =&gt; DataSet[T]`
*   `transform: DataSet[LabeledVector] =&gt; DataSet[LabeledVector]`

## Parameters

The standard scaler implementation can be controlled by the following two parameters:

| Parameters | Description |
| --- | --- |
| **Mean** | The mean of the scaled data set. (Default value: **0.0**) |
| **Std** | The standard deviation of the scaled data set. (Default value: **1.0**) |

## Examples



```
// Create standard scaler transformer val scaler = StandardScaler()
.setMean(10.0)
.setStd(2.0)

// Obtain data set to be scaled val dataSet: DataSet[Vector] = ...

// Learn the mean and standard deviation of the training data scaler.fit(dataSet)

// Scale the provided data set to have mean=10.0 and std=2.0 val scaledDS = scaler.transform(dataSet)
```



