# Feature Engineering For Machine Learning

## What is feature engineering?

Feature engineering is the act of extracting features from raw data and transforming them into formats that are suitable for the machine learn‐ ing model.

If there are too many features, or if most of them are irrelevant, then the model will be more expen‐ sive and tricky to train.

## What means good features?

Good features should not only represent salient aspects of the data, but also conform to the assumptions of the model.

$\rightarrow$ Transformations are often necessary.

## How to check?

1. whether the magnitude matters
2. consider the scale of the features
1. min-max scaling
2. standardization(but don’t center sparse data, computational burden)
3. $\ell^{2}$ normalization
3. consider the distribution of numeric features. linear function assumes the gaussian distribution(use log transforms)
4. data integration

### Book

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