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pandas python

python - pandas 分组汇总

发布于 2020-03-30 21:50:35

从我之前的问题开始:使用Pandas从数组中获取分组信息

我有一个像这样的数据集,我想通过大 pandas 获取此信息:对于每一天(按日分组),第二个值是“打开”,第二个值是“关闭”,最高值是“高” ”和“低”的下限值以及“体积”之和。

"Date","Time","Open","High","Low","Close","Up","Down","Volume"
01/03/2000,00:05,1481.50,1481.50,1481.00,1481.00,2,0,0.00
01/03/2000,00:10,1480.75,1480.75,1480.75,1480.75,1,0,1.00
01/03/2000,00:20,1480.50,1480.50,1480.50,1480.50,1,0,1.00
[...]
03/01/2018,11:05,2717.25,2718.00,2708.50,2709.25,9935,15371,25306.00
03/01/2018,11:10,2709.25,2711.75,2706.50,2709.50,8388,8234,16622.00
03/01/2018,11:15,2709.25,2711.50,2708.25,2709.50,4738,4703,9441.00
03/01/2018,11:20,2709.25,2709.50,2706.00,2707.25,3609,4685,8294.00

在我之前的问题中,用户建议我使用此方法:

df.groupby('Date').agg({
'Close': 'last',
'Open': 'first',
'High': 'max',
'Low': 'min',
'Volume': 'sum'

})

但是现在我想将第二个元素用于“打开”,将倒数第二个用于“关闭”。我怎样才能做到这一点?

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提问者
Steve
被浏览
15
jezrael 2020-01-31 19:47

您可以创建自定义函数,只有在第二个val不存在(例如NaN,第一个值)的情况下,才需要指定输出x.iat[0]

def second(x):
    return x.iat[1] if len(x) > 1 else np.nan

def secondLast(x):
    return x.iat[-2] if len(x) > 1 else np.nan

df1 = df.groupby('Date').agg({
'Close': secondLast,
'Open': second,
'High': 'max',
'Low': 'min',
'Volume': 'sum'

})

print (df1)
              Close     Open    High     Low   Volume
Date                                                 
01/03/2000  1480.75  1480.75  1481.5  1480.5      2.0
03/01/2018  2709.50  2709.25  2718.0  2706.0  59663.0