利用Pandas加载CSV文件

1. Pandas库的DataFrame类型

index -> 行索引，colum -> 列索引

索引操作：

[ ] 索引colum，.loc[ ] 索引index
例：

dict = {'one': [1, 2, 3], 'two': [4, 5, 6]}
data = pd.DataFrame(dict, index=['a', 'b', 'c'])

one two
a 1 4
b 2 5
c 3 6

data['one']

a 1
b 2
c 3
Name: one, dtype: int64

data.loc['a']

one 1
two 4
Name: a, dtype: int64

2. 用pandas 读取csv，将其拆分为特征 X 和标签 Y，并将它们转变为NumPy数组

import pandas as pd
import numpy as np

data = pd.read_csv("data.csv")

# Separate the features and the labels into arrays called X and y

X = np.array(data[['x1', 'x2']])
Y = np.array(data['y'])