Pandas 以索引列为条件

Question

我有一个 Pandas DataFrame，并将索引设置为 DateTime 列:

data['DateTime'] = pandas.to_datetime (data['DateTime'])
data = data.set_index('DateTime')

我需要插入数据。然而，这个索引后来阻止我做

data = data[pandas.to_datetime (data['DateTime']) <= cutoff]

哪里 cutoff是一些日期时间。我该怎么办？

Answer 1

看来你需要.index比较 DatetimeIndex :

data['DateTime'] = pandas.to_datetime (data['DateTime'])
data = data.set_index('DateTime')
data = data[data.index <= cutoff]

也是排序 DatetimeIndex使用 loc :

data1 = data1.loc[:cutoff]

样本:

rng = pd.date_range('2017-04-03', periods=10)
data = pd.DataFrame({'a': range(10)}, index=rng)  
print (data)
            a
2017-04-03  0
2017-04-04  1
2017-04-05  2
2017-04-06  3
2017-04-07  4
2017-04-08  5
2017-04-09  6
2017-04-10  7
2017-04-11  8
2017-04-12  9

cutoff = '2017-04-08'
data1 = data[data.index <= cutoff]
print (data1)
            a
2017-04-03  0
2017-04-04  1
2017-04-05  2
2017-04-06  3
2017-04-07  4
2017-04-08  5

data1 = data1.loc[:cutoff]
print (data1)
            a
2017-04-03  0
2017-04-04  1
2017-04-05  2
2017-04-06  3
2017-04-07  4
2017-04-08  5

谢谢 piRSquared :

data1 = data1[:cutoff]
print (data1)
            a
2017-04-03  0
2017-04-04  1
2017-04-05  2
2017-04-06  3
2017-04-07  4
2017-04-08  5