從熊貓創建numpy NAN DataFrame

Question

查看以下示例以說明如何通過DataFrame創建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 

嘗試複製方法如下：

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>爲什麼不能在這裏工作嗎？

Answer 1

因爲您的列state包含字符串，並且將字符串乘以NaN會產生錯誤。如果您確實想將狀態設置爲NaN，請使用frame['state'] = np.NAN。