要根据日期偏移量选择时间序列的第一段,请使用first () 方法。首先,使用周期和频率参数设置日期索引。Freq 用于频率 -
i = pd.date_range('2021-07-15', periods=5, freq='3D')
现在,创建一个具有上述索引的 DataFrame -
dataFrame = pd.DataFrame({'k': [1, 2, 3, 4, 5]}, index=i)
从前 4 天获取行,即 4D -
dataFrame.first('4D')
以下是完整的代码 -
import pandas as pd # date index set with 5 periods and frequency of 3 days i = pd.date_range('2021-07-15', periods=5, freq='3D') # creating DataFrame with above index dataFrame = pd.DataFrame({'k': [1, 2, 3, 4, 5]}, index=i) print"DataFrame...\n",dataFrame # fetching initial few rows # fetch rows from the first 4 days print"First few rows fetched..\n",dataFrame.first('4D');输出结果
这将产生以下输出 -
DataFrame... k 2021-07-15 1 2021-07-18 2 2021-07-21 3 2021-07-24 4 2021-07-27 5 First few rows fetched.. k 2021-07-15 1 2021-07-18 2