How to fill missing values relative to a value from another column - python-3.x

Question

I'd like to fill missing values with conditions relative to the country:
For example, I'd want to replace China's missing values with the mean of Age and for USA it's the median of Age. For now, I don't want to touch of EU's missing values.
How could I do realise it ?
Below the dataframe
import pandas as pd
data = [['USA', ], ['EU', 15], ['China', 35],
['USA', 45], ['EU', 30], ['China', ],
['USA', 28], ['EU', 26], ['China', 78],
['USA', 65], ['EU', 53], ['China', 66],
['USA', 32], ['EU', ], ['China', 14]]
# Create the pandas DataFrame
df = pd.DataFrame(data, columns = ['Country', 'Age'])
df.head(10)
Country Age
0 USA NaN
1 EU 15.0
2 China 35.0
3 USA 45.0
4 EU 30.0
5 China NaN
6 USA 28.0
7 EU 26.0
8 China 78.0
9 USA 65.0
10 EU NaN
Thank you

Answer 1

Not sure if this is the best way to do it but it is one way to do it
age_series = df['Age'].copy()
df.loc[(df['Country'] == 'China') & (df['Age'].isnull()), 'Age'] = age_series.mean()
df.loc[(df['Country'] == 'USA') & (df['Age'].isnull()), 'Age'] = age_series.median()
Note that I copied the age column before hand so that you get the median of the original age series not after calculating the mean for the US. This is the final results
Country Age
0 USA 33.500000
1 EU 15.000000
2 China 35.000000
3 USA 45.000000
4 EU 30.000000
5 China 40.583333
6 USA 28.000000
7 EU 26.000000
8 China 78.000000
9 USA 65.000000
10 EU 53.000000
11 China 66.000000
12 USA 32.000000
13 EU NaN
14 China 14.000000

Answer 2

May be you can try this
df['Age']=(np.where((df['Country'] == 'China') & (df['Age'].isnull()),df['Age'].mean()
,np.where((df['Country'] == 'USA') & (df['Age'].isnull()),df['Age'].median(),df['Age']))).round()
Output
Country Age
0 USA 34.0
1 EU 15.0
2 China 35.0
3 USA 45.0
4 EU 30.0
5 China 41.0
6 USA 28.0
7 EU 26.0
8 China 78.0
9 USA 65.0
10 EU 53.0
11 China 66.0
12 USA 32.0
13 EU NaN
14 China 14.0

Answer 3

IIUC, we can create a function to handle this as it's not easily automated (although I may be wrong)
the idea is to pass in the country name & fill type (i.e mean median) you can extend the function to add in your agg types.
it returns a data frame that modifies yours, so you can use this to assign it back to your col
def missing_values(dataframe,country,fill_type):
"""
takes 3 arguments, dataframe, country & fill_type:
fill_type is the method used to fill `NA` values, mean, median, etc.
"""
fill_dict = dataframe.loc[dataframe['Country'] == country]\
.groupby("Country")["Age"].agg(
["mean", "median"]).to_dict(orient='index')
dataframe.loc[dataframe['Country'] == country, 'Age'] \
= dataframe['Age'].fillna(fill_dict[country][fill_type])
return dataframe
print(missing_values(df,'China','mean')
Country Age
0 USA NaN
1 EU 15.00
2 China 35.00
3 USA 45.00
4 EU 30.00
5 China 48.25
6 USA 28.00
7 EU 26.00
8 China 78.00
9 USA 65.00
10 EU 53.00
11 China 66.00
12 USA 32.00
13 EU NaN
14 China 14.00
print(missing_values(df,'USA','median'))
Country Age
0 USA 38.50
1 EU 15.00
2 China 35.00
3 USA 45.00
4 EU 30.00
5 China 48.25
6 USA 28.00
7 EU 26.00
8 China 78.00
9 USA 65.00
10 EU 53.00
11 China 66.00
12 USA 32.00
13 EU NaN
14 China 14.00