在Python / Pandas中重新排列数据：将特定的列vlaues转换为标题

Question

I have been given a large dataset that has data arranged like so:

location  cost    year
1         23.15    1986
1         23.91    1988
1         23.31    1989
1         23.91    1993
1         22.98    1994
1         23.99    1995
1         23.71    1997
1         23.01    1999
2         23.21    2000
2         24.28    2004
2         24.4     2005

I'd like to rearrange this so it is in the form:

location    1985    1986    1987   1988
1           20.00   20.00   20.0    20.0
2           20.00   20.00   20.0    20.0
3           20.00   20.00   20.0    20.0
4           20.00   20.00   20.0    20.0
5           20.00   20.00   20.0    20.0

(note: ignore that the new costs are all 20.0. My goal is to turn the values within the year column into headers, so that each location is only listed once, with the cost for a specific year located in that column.)

Is there a straightforward way to do this? I've looked into groupy and transpose but have not been able to produce anything close to what I'd like.

Thank you in advance for any pointers you can provide.

Answer 1

You need to use pivot_table :

pd.pivot_table(df, index='location', columns='year', values='cost', fill_value=0)

With your sample:

#Out[11]: 
#year       1986   1988   1989   1993   1994   1995   1997   1999   2000  \
#location                                                                  
#1         23.15  23.91  23.31  23.91  22.98  23.99  23.71  23.01   0.00   
#2          0.00   0.00   0.00   0.00   0.00   0.00   0.00   0.00  23.21   

#year       2004  2005  
#location               
#1          0.00   0.0  
#2         24.28  24.4