问用Python重组Dataframe
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Stack Overflow用户

提问于 2015-06-17 09:25:46

回答 1查看 756关注 0票数 2

我已经从此Excel文件中的倒数第二个工作表中收集了数据，以及从5.5岁开始的最后一个工作表中的所有数据。我有密码能做到这一点。但是，我现在希望对dataframe进行结构调整，使其具有以下列，并且很难做到这一点：

我的密码在下面。

import urllib2
import pandas as pd
import os
import xlrd 

url = 'http://www.bankofengland.co.uk/statistics/Documents/yieldcurve/uknom05_mdaily.xls'
socket = urllib2.urlopen(url)

xd = pd.ExcelFile(socket)

#Had to do this based on actual sheet_names rather than index as there are some extra sheet names in xd.sheet_names
df1 = xd.parse('4. spot curve', header=None)
df1 = df1.loc[:, df1.loc[3, :] >= 5.5] #Assumes the maturity is always on the 4th line of the sheet
df2 = xd.parse('3. spot, short end', header=None)

bigdata = df1.append(df2,ignore_index = True)

编辑：Dataframe当前如下所示。不幸的是，当前的Dataframe相当混乱：

                       0    1   2   3         4         5         6   \
0                     NaN  NaN NaN NaN       NaN       NaN       NaN   
1                     NaN  NaN NaN NaN       NaN       NaN       NaN   
2                Maturity  NaN NaN NaN       NaN       NaN       NaN   
3                  years:  NaN NaN NaN       NaN       NaN       NaN   
4                     NaN  NaN NaN NaN       NaN       NaN       NaN   
5     2005-01-03 00:00:00  NaN NaN NaN       NaN       NaN       NaN   
6     2005-01-04 00:00:00  NaN NaN NaN       NaN       NaN       NaN
...                   ...  ...  ..  ..       ...       ...       ...   
5410  2015-04-20 00:00:00  NaN NaN NaN       NaN  0.367987  0.357069   
5411  2015-04-21 00:00:00  NaN NaN NaN       NaN  0.362478  0.352581

它有5440行和61列

但是，我希望数据格式是：

我认为列1,2,3,4,5和6包含收益率曲线数据。但是，我不确定与“成熟度年”相关的数据在当前DataFrame中的位置。

Date(which is the 2nd Column in the current Dataframe)    Update time(which would just be a column with datetime.datetime.now())    Currency(which would just be a column with 'GBP')    Maturity Date    Yield Data from SpreadSheet

dataframe

python

pandas

回答 1

Stack Overflow用户

回答已采纳

发布于 2015-06-17 13:47:45

我使用pandas.io.excel.read_excel函数从url读取xls。以下是清理英国收益率曲线数据集的一种方法。

注意:通过应用函数执行三次样条插值需要相当长的时间(在我的PC上大约2分钟)。它从大约100点插入到300点，逐行(总共2638点)。

from pandas.io.excel import read_excel
import pandas as pd
import numpy as np

url = 'http://www.bankofengland.co.uk/statistics/Documents/yieldcurve/uknom05_mdaily.xls'

# check the sheet number, spot: 9/9, short end 7/9
spot_curve = read_excel(url, sheetname=8)
short_end_spot_curve = read_excel('uknom05_mdaily.xls', sheetname=6)

# preprocessing spot_curve
# ==============================================
# do a few inspection on the table
spot_curve.shape
spot_curve.iloc[:, 0]
spot_curve.iloc[:, -1]
spot_curve.iloc[0, :]
spot_curve.iloc[-1, :]
# do some cleaning, keep NaN for now, as forward fill NaN is not recommended for yield curve
spot_curve.columns = spot_curve.loc['years:']
spot_curve.columns.name = 'years'
valid_index = spot_curve.index[4:]
spot_curve = spot_curve.loc[valid_index]
# remove all maturities within 5 years as those are duplicated in short-end file
col_mask = spot_curve.columns.values > 5
spot_curve = spot_curve.iloc[:, col_mask]

# now spot_curve is ready, check it
spot_curve.head()
spot_curve.tail()
spot_curve.shape

spot_curve.shape
Out[184]: (2715, 40)

# preprocessing short end spot_curve
# ==============================================
short_end_spot_curve.columns = short_end_spot_curve.loc['years:']
short_end_spot_curve.columns.name = 'years'
valid_index = short_end_spot_curve.index[4:]
short_end_spot_curve = short_end_spot_curve.loc[valid_index]
short_end_spot_curve.head()
short_end_spot_curve.tail()
short_end_spot_curve.shape

short_end_spot_curve.shape
Out[185]: (2715, 60)

# merge these two, time index are identical
# ==============================================
combined_data = pd.concat([short_end_spot_curve, spot_curve], axis=1, join='outer')
# sort the maturity from short end to long end
combined_data.sort_index(axis=1, inplace=True)

combined_data.head()
combined_data.tail()
combined_data.shape

# deal with NaN: the most sound approach is fit the non-arbitrage NSS curve
# however, this is not currently supported in python.
# do a cubic spline instead
# ==============================================

# if more than half of the maturity points are NaN, then interpolation is likely to be unstable, so I'll remove all rows with NaNs count greater than  50
def filter_func(group):
    return group.isnull().sum(axis=1) <= 50

combined_data = combined_data.groupby(level=0).filter(filter_func)
# no. of rows down from 2715 to 2628
combined_data.shape

combined_data.shape
Out[186]: (2628, 100)


from scipy.interpolate import interp1d

# mapping points, monthly frequency, 1 mon to 25 years
maturity = pd.Series((np.arange(12 * 25) + 1) / 12)
# do the interpolation day by day
key = lambda x: x.date
by_day = combined_data.groupby(level=0)

# write out apply function
def interpolate_maturities(group):
    # transpose row vector to column vector and drops all nans
    a = group.T.dropna().reset_index()
    f = interp1d(a.iloc[:, 0], a.iloc[:, 1], kind='cubic', bounds_error=False, assume_sorted=True)
    return pd.Series(maturity.apply(f).values, index=maturity.values)

# this may take a while .... apply provides flexibility but spead is not good
cleaned_spot_curve = by_day.apply(interpolate_maturities)

# a quick look on the data
cleaned_spot_curve.iloc[[1,1000, 2000], :].T.plot(title='Cross-Maturity Yield Curve')
cleaned_spot_curve.iloc[:, [23, 59, 119]].plot(title='Time-Series')