Pandas重采样错误：仅对DatetimeIndex或PeriodIndex有效

Question

在DataFrame上使用panda的resample函数以将tick数据转换为OHLCV时，会遇到重采样错误。

我们应该如何解决错误？

data = pd.read_csv('tickdata.csv', header=None, names=['Timestamp','Price','Volume']).set_index('Timestamp')
data.head()

# Resample data into 30min bins
ticks = data.ix[:, ['Price', 'Volume']]
bars = ticks.Price.resample('30min', how='ohlc')
volumes = ticks.Volume.resample('30min', how='sum')

这给出了错误：

TypeError: Only valid with DatetimeIndex or PeriodIndex

Answer 1

将索引中的整数时间戳转换为DatetimeIndex：

data.index = pd.to_datetime(data.index, unit='s')

这将整数解释为自纪元以来的秒数。

例如，给定

data = pd.DataFrame(
    {'Timestamp':[1313331280, 1313334917, 1313334917, 1313340309, 1313340309], 
     'Price': [10.4]*3 + [10.5]*2, 'Volume': [0.779, 0.101, 0.316, 0.150, 1.8]})
data = data.set_index(['Timestamp'])
#             Price  Volume
# Timestamp                
# 1313331280   10.4   0.779
# 1313334917   10.4   0.101
# 1313334917   10.4   0.316
# 1313340309   10.5   0.150
# 1313340309   10.5   1.800

data.index = pd.to_datetime(data.index, unit='s')

产量

                     Price  Volume
2011-08-14 14:14:40   10.4   0.779
2011-08-14 15:15:17   10.4   0.101
2011-08-14 15:15:17   10.4   0.316
2011-08-14 16:45:09   10.5   0.150
2011-08-14 16:45:09   10.5   1.800

然后

ticks = data.ix[:, ['Price', 'Volume']]
bars = ticks.Price.resample('30min').ohlc()
volumes = ticks.Volume.resample('30min').sum()

可以计算：

In [368]: bars
Out[368]: 
                     open  high   low  close
2011-08-14 14:00:00  10.4  10.4  10.4   10.4
2011-08-14 14:30:00   NaN   NaN   NaN    NaN
2011-08-14 15:00:00  10.4  10.4  10.4   10.4
2011-08-14 15:30:00   NaN   NaN   NaN    NaN
2011-08-14 16:00:00   NaN   NaN   NaN    NaN
2011-08-14 16:30:00  10.5  10.5  10.5   10.5

In [369]: volumes
Out[369]: 
2011-08-14 14:00:00    0.779
2011-08-14 14:30:00      NaN
2011-08-14 15:00:00    0.417
2011-08-14 15:30:00      NaN
2011-08-14 16:00:00      NaN
2011-08-14 16:30:00    1.950
Freq: 30T, Name: Volume, dtype: float64