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数据归一化的方式
from sklearn.preprocessing import MinMaxScaler
最值归一化 normalization :把所有数据映射到0-1之间 适用于分布有明显边界的情况
from sklearn.preprocessing import StandardScaler
均值方差归一化 standardization :把所有数据归一化到均值为0 方差为1的分布中 没有明显的边界的情况也适用
- import numpy as np
- class StandardScaler:
- def __init__(self):
- self.mean_ = None
- self.scale_ = None
- def fit(self, X):
- """根据训练数据集X获得数据的均值和方差"""
- assert X.ndim == 2, "The dimension of X must be 2"
- self.mean_ = np.array([np.mean(X[:,i]) for i in range(X.shape[1])])
- self.scale_ = np.array([np.std(X[:,i]) for i in range(X.shape[1])])
- return self
- def transform(self, X):
- """将X根据这个StandardScaler进行均值方差归一化处理"""
- assert X.ndim == 2, "The dimension of X must be 2"
- assert self.mean_ is not None and self.scale_ is not None, \
- "must fit before transform!"
- assert X.shape[1] == len(self.mean_), \
- "the feature number of X must be equal to mean_ and std_"
- resX = np.empty(shape=X.shape, dtype=float)
- for col in range(X.shape[1]):
- resX[:,col] = (X[:,col] - self.mean_[col]) / self.scale_[col]
- return resX
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