[英]Pandas inverse of pivot table
I have a DataFrame (eg, df_p
) which has already converted into a pivot table:我有一个已经转换为数据透视表的 DataFrame(例如
df_p
):
import pandas as pd
df = pd.DataFrame({'start_year':[2000, 2001, 2002],
'end_year':[2010, 2011, 2012],
'price':[1.0, 2.0, 3.0]})
# end_year price start_year
# 0 2010 1.0 2000
# 1 2011 2.0 2001
# 2 2012 3.0 2002
df_p = df.pivot('start_year', 'end_year', 'price')
# end_year 2010 2011 2012
# start_year
# 2000 1.0 NaN NaN
# 2001 NaN 2.0 NaN
# 2002 NaN NaN 3.0
How should I convert df_p
back to df
?我应该如何将
df_p
转换回df
?
stack
df_p.stack().reset_index(name='price')
start_year end_year price
0 2000 2010 1.0
1 2001 2011 2.0
2 2002 2012 3.0
melt
+ dropna
melt
+ dropna
(can't guarantee this works in every case, however) (但是,不能保证这在所有情况下都有效)
df_p.reset_index().melt('start_year', value_name='price').dropna()
start_year end_year price
0 2000 2010 1.0
4 2001 2011 2.0
8 2002 2012 3.0
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