从熊猫创建numpy NAN DataFrame

Question

查看以下示例以说明如何通过DataFrame创建NAN。

import pandas as pd 
import numpy as np 
import math 
import copy 
import QSTK.qstkutil.qsdateutil as du 
import datetime as dt 
import QSTK.qstkutil.DataAccess as da 
import QSTK.qstkutil.tsutil as tsu 
import QSTK.qstkstudy.EventProfiler as ep 

""" 
Accepts a list of symbols along with start and end date 
Returns the Event Matrix which is a pandas Datamatrix 
Event matrix has the following structure : 
    |IBM |GOOG|XOM |MSFT| GS | JP | 
(d1)|nan |nan | 1 |nan |nan | 1 | 
(d2)|nan | 1 |nan |nan |nan |nan | 
(d3)| 1 |nan | 1 |nan | 1 |nan | 
(d4)|nan | 1 |nan | 1 |nan |nan | 
................................... 
................................... 
Also, d1 = start date 
nan = no information about any event. 
1 = status bit(positively confirms the event occurence) 
""" 

def find_events(ls_symbols, d_data): 
    ''' Finding the event dataframe ''' 
    df_close = d_data['actual_close'] 
    ts_market = df_close['SPY'] 

    print "Finding Events" 

    # Creating an empty dataframe 
    df_events = copy.deepcopy(df_close) # type <class 'pandas.core.frame.DataFrame'> 
    df_events = df_events * np.NAN # << why it works here 

尝试复制方法如下：

import numpy as np 
import pandas as pd 
from pandas import Series, DataFrame 

data = {'state': ['Ohio', 'Ohio', 'Ohio', 'Nevada', 'Nevada'], 
     'year': [2000, 2001, 2002, 2001, 2002], 
     'pop': [1.5, 1.7, 3.6, 2.4, 2.9]} 
frame = DataFrame(data) 
frame = frame * np.NAN # TypeError: can't multiply sequence by non-int of type 'float' 

Q>为什么不能在这里工作吗？

Answer 1

因为您的列state包含字符串，并且将字符串乘以NaN会产生错误。如果您确实想将状态设置为NaN，请使用frame['state'] = np.NAN。