I have two data frames that I would eventually like to merge in order to compare differences between alternative spellings of leader names.
My first dataframe looks something like the following:
year country_isocode country_name leader leader_start_date leader_end_date
20 1986 AFG Afghanistan Mohammed Najibullah 1986-05-04 1992-04-16
21 1987 AFG Afghanistan Mohammed Najibullah 1986-05-04 1992-04-16
22 1988 AFG Afghanistan Mohammed Najibullah 1986-05-04 1992-04-16
23 1989 AFG Afghanistan Mohammed Najibullah 1986-05-04 1992-04-16
24 1990 AFG Afghanistan Mohammed Najibullah 1986-05-04 1992-04-16
25 1991 AFG Afghanistan Mohammed Najibullah 1986-05-04 1992-04-16
26 1992 AFG Afghanistan Burhanuddin Rabbani 1992-06-28 1996-09-27
27 1993 AFG Afghanistan Burhanuddin Rabbani 1992-06-28 1996-09-27
28 1994 AFG Afghanistan Burhanuddin Rabbani 1992-06-28 1996-09-27
While my second looks like this:
leader_start_date leader_end_date LeaderCountryOrIGO LeaderCountryISO LeaderTitle LeaderLastName LeaderFullName
0 1986-05-04 1990-06-28 Afghanistan AFG General Secretary Najibullah Mohammad Najibullah
1 1989-02-21 1990-05-07 Afghanistan AFG Prime Minister Keshtmand Ali Keshtmand
2 1990-05-07 1992-04-15 Afghanistan AFG Prime Minister Khaliqyar Fazal Haq Khaliqyar
3 1992-04-16 1992-04-28 Afghanistan AFG President (Acting) Hatef Abdul Rahim Hatef
4 1992-04-28 1992-06-28 Afghanistan AFG President (Acting) Mojadedi Sibghatullah Mojadedi
5 1992-06-28 1996-09-27 Afghanistan AFG President Rabbani Burhanuddin Rabbani
The first data frame has individual rows for every country-year entry in the dataset while the second data frame has a single row for a unique leader with their range of years in office. My goal is to re-shape the second data frame so that it is comparable to the shape of the first.
I would like to take the year range implied by the two datetime columns "leader_start_date, "leader_end_date" in the second data set and "expand" these to create sets of new rows for every year in that range which include duplicate information regarding country and leader name. I would then need to iterate this solution for all unique leader names and their year ranges in the second date frame.
While the data sets aren't a perfect match, getting both data frames in the same shape will allow me to identify a number of matches.
CodePudding user response:
Use:
#convert both columns to datetimes
df['leader_start_date'] = pd.to_datetime(df['leader_start_date'])
df['leader_end_date'] = pd.to_datetime(df['leader_end_date'])
#create new column by years
df.insert(0, 'year', df['leader_start_date'].dt.year)
#subtract years for repeating, repalce missing values by actual year
s = df['leader_end_date'].dt.year.fillna(pd.to_datetime('now').year) - df['year']
#if output is previous year by leader_end_date
df = df.loc[df.index.repeat(s)].copy()
#if output match also year in leader_end_date
# df = df.loc[df.index.repeat(s 1)].copy()
#add counter to column year
df['year'] = df.groupby(level=0).cumcount()
#create default index
df = df.reset_index(drop=True)
print (df)
year leader_start_date leader_end_date LeaderCountryOrIGO \
0 1986 1986-05-04 1990-06-28 Afghanistan
1 1987 1986-05-04 1990-06-28 Afghanistan
2 1988 1986-05-04 1990-06-28 Afghanistan
3 1989 1986-05-04 1990-06-28 Afghanistan
4 1989 1989-02-21 1990-05-07 Afghanistan
5 1990 1990-05-07 1992-04-15 Afghanistan
6 1991 1990-05-07 1992-04-15 Afghanistan
7 1992 1992-06-28 1996-09-27 Afghanistan
8 1993 1992-06-28 1996-09-27 Afghanistan
9 1994 1992-06-28 1996-09-27 Afghanistan
10 1995 1992-06-28 1996-09-27 Afghanistan
LeaderCountryISO LeaderTitle LeaderLastName LeaderFullName
0 AFG General Secretary Najibullah Mohammad Najibullah
1 AFG General Secretary Najibullah Mohammad Najibullah
2 AFG General Secretary Najibullah Mohammad Najibullah
3 AFG General Secretary Najibullah Mohammad Najibullah
4 AFG Prime Minister Keshtmand Ali Keshtmand
5 AFG Prime Minister Khaliqyar Fazal Haq Khaliqyar
6 AFG Prime Minister Khaliqyar Fazal Haq Khaliqyar
7 AFG President Rabbani Burhanuddin Rabbani
8 AFG President Rabbani Burhanuddin Rabbani
9 AFG President Rabbani Burhanuddin Rabbani
10 AFG President Rabbani Burhanuddin Rabbani