πŸ“ƒ Solution for Exercise M6.01#

The aim of this notebook is to investigate if we can tune the hyperparameters of a bagging regressor and evaluate the gain obtained.

We will load the California housing dataset and split it into a training and a testing set.

from sklearn.datasets import fetch_california_housing
from sklearn.model_selection import train_test_split

data, target = fetch_california_housing(as_frame=True, return_X_y=True)
target *= 100  # rescale the target in k$
data_train, data_test, target_train, target_test = train_test_split(
    data, target, random_state=0, test_size=0.5)

Note

If you want a deeper overview regarding this dataset, you can refer to the Appendix - Datasets description section at the end of this MOOC.

Create a BaggingRegressor and provide a DecisionTreeRegressor to its parameter base_estimator. Train the regressor and evaluate its generalization performance on the testing set using the mean absolute error.

# solution
from sklearn.metrics import mean_absolute_error
from sklearn.tree import DecisionTreeRegressor
from sklearn.ensemble import BaggingRegressor

tree = DecisionTreeRegressor()
bagging = BaggingRegressor(base_estimator=tree, n_jobs=2)
bagging.fit(data_train, target_train)
target_predicted = bagging.predict(data_test)
print(f"Basic mean absolute error of the bagging regressor:\n"
      f"{mean_absolute_error(target_test, target_predicted):.2f} k$")
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
Basic mean absolute error of the bagging regressor:
36.83 k$

Now, create a RandomizedSearchCV instance using the previous model and tune the important parameters of the bagging regressor. Find the best parameters and check if you are able to find a set of parameters that improve the default regressor still using the mean absolute error as a metric.

Tip

You can list the bagging regressor’s parameters using the get_params method.

# solution
for param in bagging.get_params().keys():
    print(param)
base_estimator__ccp_alpha
base_estimator__criterion
base_estimator__max_depth
base_estimator__max_features
base_estimator__max_leaf_nodes
base_estimator__min_impurity_decrease
base_estimator__min_samples_leaf
base_estimator__min_samples_split
base_estimator__min_weight_fraction_leaf
base_estimator__random_state
base_estimator__splitter
base_estimator
bootstrap
bootstrap_features
estimator
max_features
max_samples
n_estimators
n_jobs
oob_score
random_state
verbose
warm_start
from scipy.stats import randint
from sklearn.model_selection import RandomizedSearchCV

param_grid = {
    "n_estimators": randint(10, 30),
    "max_samples": [0.5, 0.8, 1.0],
    "max_features": [0.5, 0.8, 1.0],
    "base_estimator__max_depth": randint(3, 10),
}
search = RandomizedSearchCV(
    bagging, param_grid, n_iter=20, scoring="neg_mean_absolute_error"
)
_ = search.fit(data_train, target_train)
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/sklearn/ensemble/_base.py:166: FutureWarning: `base_estimator` was renamed to `estimator` in version 1.2 and will be removed in 1.4.
  warnings.warn(
import pandas as pd

columns = [f"param_{name}" for name in param_grid.keys()]
columns += ["mean_test_error", "std_test_error"]
cv_results = pd.DataFrame(search.cv_results_)
cv_results["mean_test_error"] = -cv_results["mean_test_score"]
cv_results["std_test_error"] = cv_results["std_test_score"]
cv_results[columns].sort_values(by="mean_test_error")
param_n_estimators param_max_samples param_max_features param_base_estimator__max_depth mean_test_error std_test_error
3 20 1.0 1.0 9 39.287032 1.176986
2 13 0.8 1.0 9 39.763999 0.995976
16 10 0.8 1.0 9 39.979491 1.132505
1 26 1.0 0.8 8 40.380609 0.983110
19 21 0.5 0.8 8 41.371202 1.299754
7 10 0.5 0.8 9 41.818500 1.849915
5 12 0.8 1.0 7 43.135688 1.238979
11 21 0.5 0.5 8 45.203602 1.493870
10 20 1.0 1.0 6 45.409762 1.041063
9 22 0.5 0.5 8 46.999697 0.953817
8 19 1.0 0.5 7 47.094651 1.667611
4 16 0.5 0.5 6 48.472914 1.547955
14 11 0.5 0.8 5 48.483726 1.151304
0 25 1.0 0.5 6 49.792786 2.291302
17 19 1.0 1.0 4 51.731389 1.184337
15 16 0.8 1.0 4 51.790025 1.408888
13 10 1.0 1.0 4 52.280050 1.318771
12 11 0.5 0.5 4 54.856320 2.403840
18 14 1.0 1.0 3 56.910818 1.100283
6 14 0.8 0.8 3 57.674482 1.469571
target_predicted = search.predict(data_test)
print(f"Mean absolute error after tuning of the bagging regressor:\n"
      f"{mean_absolute_error(target_test, target_predicted):.2f} k$")
Mean absolute error after tuning of the bagging regressor:
39.26 k$

We see that the predictor provided by the bagging regressor does not need much hyperparameter tuning compared to a single decision tree.