数据规范化笔记
2015-07-14 21:35
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最小-最大规范化(min-max normalization)
from sklearn import preprocessing import numpy as np X_train = np.array([[1., -1., 2.], [2., 0., 0.], [0., 1., -1.]]) min_max_scaler = preprocessing.MinMaxScaler([0, 1]) X_train_minmax = min_max_scaler.fit_transform(X_train) print(min_max_scaler.scale_) print() print(X_train_minmax) X_test = np.array([[-2., -1., 4.]]) X_test_minmax = min_max_scaler.transform(X_test) print() print(X_test_minmax)
结果:
[ 0.5 0.5 0.33333333] [[ 0.5 0. 1. ] [ 1. 0.5 0.33333333] [ 0. 1. 0. ]] [[-1. 0. 1.66666667]]
z-score规范化(零-均值规范化)
from sklearn import preprocessing import numpy as np X = np.array([[ 1., -1., 2.], [ 2., 0., 0.], [ 0., 1., -1.]]) X_scaled = preprocessing.scale(X) # # X_scaled # array([[ 0. ..., -1.22..., 1.33...], # [ 1.22..., 0. ..., -0.26...], # [-1.22..., 1.22..., -1.06...]]) # Scaled data has zero mean and unit variance: # >>> mean=X_scaled.mean(axis=0)# axis=0,特征;axis=1,sample print(mean) print() # array([ 0., 0., 0.]) std=X_scaled.std(axis=0) print(std) # array([ 1., 1., 1.]) scaler = preprocessing.StandardScaler().fit(X) print("scaler.mean_:",scaler.mean_) # array([ 1. ..., 0. ..., 0.33...]) print("scaler.std_:",scaler.std_) # array([ 0.81..., 0.81..., 1.24...]) train=scaler.transform(X) print("train:",train) # array([[ 0. ..., -1.22..., 1.33...], # [ 1.22..., 0. ..., -0.26...], # [-1.22..., 1.22..., -1.06...]]) # The scaler instance can then be used on new data to transform it the same way it did on the training set: test=scaler.transform([[-1., 1., 0.]]) print("test:",test) # array([[-2.44..., 1.22..., -0.26...]])
小数定标规范化(normalization by decimal scaling)
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