Percentage of a multiindex in Pandas

Question

I need to find the percentage of a MultiIndex column ('count'). My DataFrame looks like:

            count
A  week1     264

   week2      29

B  week1     152

   week2      15

and I'd like to add a column 'percent' to make

            count percent
A  week1     264      0.9

   week2      29      0.1

B  week1     152     0.91

   week2      15     0.09

I know that I can find the totals I want by

mydf.sum(level=[0, 1])

but I can't seem to figure out how to turn this into a percentage.

Answer 1

You can do this with groupby and transform:

df['percent'] = df.groupby(level=0).transform(lambda x: (x / x.sum()).round(2))

#          count  percent
# A week1    264     0.90
#   week2     29     0.10
# B week1    152     0.91
#   week2     15     0.09

Answer 2

Without groupby

df['percentage']=df['count'].div(df['count'].sum(level=0),level=0)
df
Out[128]: 
         count  percentage
x b                       
A week1    264    0.901024
  week2     29    0.098976
B week1    152    0.910180
  week2     15    0.089820