pca python
import numpy as np
from sklearn.decomposition import PCA
pca = PCA(n_components = 3) # Choose number of components
pca.fit(X) # fit on X_train if train/test split applied
print(pca.explained_variance_ratio_)
pca python
import numpy as np
from sklearn.decomposition import PCA
pca = PCA(n_components = 3) # Choose number of components
pca.fit(X) # fit on X_train if train/test split applied
print(pca.explained_variance_ratio_)
feature scaling in python
from sklearn.preprocessing import MinMaxScaler
scaler = MinMaxScaler()
from sklearn.linear_model import Ridge
X_train, X_test, y_train, y_test = train_test_split(X_data, y_data,
random_state = 0)
X_train_scaled = scaler.fit_transform(X_train)
X_test_scaled = scaler.transform(X_test)
Scaling features to a range
# Scaling features to a range using MaxAbsScaler
X_train = np.array([[ 1., -1., 2.],
[ 2., 0., 0.],
[ 0., 1., -1.]])
max_abs_scaler = preprocessing.MaxAbsScaler()
X_train_maxabs = max_abs_scaler.fit_transform(X_train)
X_train_maxabs
# array([[ 0.5, -1., 1. ],
# [ 1. , 0. , 0. ],
# [ 0. , 1. , -0.5]])
X_test = np.array([[ -3., -1., 4.]])
X_test_maxabs = max_abs_scaler.transform(X_test)
X_test_maxabs
# array([[-1.5, -1. , 2. ]])
max_abs_scaler.scale_
# array([2., 1., 2.])
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