python - Pandas :根据开始/结束日期聚合

Question

这实际上是一个去聚合，因为我有一个这样构造的数据集:

id  type   first_year   last_year
A   t1     2009         2014
A   t1     2010         2015
B   t1     2007         2009
B   t2     2008         2011

但我需要按 id/year 进行聚合，并且有重叠的开始/结束条目。

数据在 pandas 数据框中，如下所示:

test_frame = pd.DataFrame([['A','t1',2009,2014],
                       ['A','t1',2010,2015],
                       ['B','t1',2007,2009],
                       ['B','t2',2008,2011]],
                      columns = ['id','type','first_year','last_year'])

我希望以几种不同的方式返回数据:

id  year  count
A   2009  1
A   2010  2
A   2011  2
...
B   2007  1
B   2008  2
B   2009  1 

也许像这样:

id  year  type    count
A   2009  t1      1
A   2010  t1      2
A   2011  t1      2
...
B   2007  t1      1
B   2008  t1      1
B   2008  t2      1
B   2009  t2      1
B   2010  t2      1

这基本上适用于第一种方法，但正如您可以想象的那样，对大型数据集使用 itertuples 会非常慢。还有更多 Pandas 式的方式吗？

out_frame = pd.DataFrame(columns = ['id','type','year'])
for rows in test_frame.itertuples():
    for year in range(int(rows[3]),int(rows[4])):
        d2 = pd.DataFrame({'id': [rows[1]],'year': [year]},columns = ['id','year'])
        out_frame = out_frame.append(d2)
output1 = out_frame.groupby(['id','year'])['year'].count()
output1

Answer 1

您可以使用 stack和 resample :

import pandas as pd

test_frame = pd.DataFrame([['A','t1',2009,2014],
                       ['A','t1',2010,2015],
                       ['B','t1',2007,2009],
                       ['B','t2',2008,2011]],
                      columns = ['id','type','first_year','last_year'])

print test_frame
  id type  first_year  last_year
0  A   t1        2009       2014
1  A   t1        2010       2015
2  B   t1        2007       2009
3  B   t2        2008       2011

#stack df, drop and rename column year
test_frame = test_frame.set_index(['id','type'], append=True).stack().reset_index(level=[1,2,3])
test_frame = test_frame.drop('level_3', axis=1).rename(columns={0:'year'})
#convert year to datetime
test_frame['year'] = pd.to_datetime(test_frame['year'], format="%Y")
print test_frame
  id type       year
0  A   t1 2009-01-01
0  A   t1 2014-01-01
1  A   t1 2010-01-01
1  A   t1 2015-01-01
2  B   t1 2007-01-01
2  B   t1 2009-01-01
3  B   t2 2008-01-01
3  B   t2 2011-01-01

#resample and fill missing data 
out_frame = test_frame.groupby(test_frame.index).apply(lambda x: x.set_index('year').resample('1AS', how='first',fill_method='ffill')).reset_index(level=1)
print out_frame
        year id type
0 2009-01-01  A   t1
0 2010-01-01  A   t1
0 2011-01-01  A   t1
0 2012-01-01  A   t1
0 2013-01-01  A   t1
0 2014-01-01  A   t1
1 2010-01-01  A   t1
1 2011-01-01  A   t1
1 2012-01-01  A   t1
1 2013-01-01  A   t1
1 2014-01-01  A   t1
1 2015-01-01  A   t1
2 2007-01-01  B   t1
2 2008-01-01  B   t1
2 2009-01-01  B   t1
3 2008-01-01  B   t2
3 2009-01-01  B   t2
3 2010-01-01  B   t2
3 2011-01-01  B   t2

#convert to year
out_frame['year'] = out_frame['year'].dt.year

output1 = out_frame.groupby(['id','year', 'type'])['year'].count().reset_index(name='count')
print output1
   id  year type  count
0   A  2009   t1      1
1   A  2010   t1      2
2   A  2011   t1      2
3   A  2012   t1      2
4   A  2013   t1      2
5   A  2014   t1      2
6   A  2015   t1      1
7   B  2007   t1      1
8   B  2008   t1      1
9   B  2008   t2      1
10  B  2009   t1      1
11  B  2009   t2      1
12  B  2010   t2      1
13  B  2011   t2      1

output2 = out_frame.groupby(['id','year'])['year'].count().reset_index(name='count')
print output2
   id  year  count
0   A  2009      1
1   A  2010      2
2   A  2011      2
3   A  2012      2
4   A  2013      2
5   A  2014      2
6   A  2015      1
7   B  2007      1
8   B  2008      2
9   B  2009      2
10  B  2010      1
11  B  2011      1