# Models in Pipelines

Jul 04, 2019

## Pipeline are useful for model building

Data transfromation is a key step in any ML problem. It can quickly become cumbersome and error prone if this is done by hand. Scikit-learn gives the *pipeline* object to solve this problem.

Let’s say in a given problem, we would like to do the following:

- Impute missing values using the mean
- Transform features to quadratic
- Fit a lineear regression

## Example

```
from sklearn.pipeline import make_pipeline
model = make_pipeline(Imputer(strategy='mean'),
PolynomialFeatures(degree=2),
LinearRegression()
)
```

The pipeline object behaves like a Sklearn object and can take the *fit* and *predict* steps.

```
model.fit(X, y)
pred = model.predict(X)
```

We could apply GridSearch for Hyperparameters selection on this pipeline object do get the best performing model.