How can i fill nan values in a df using group mean?

Question

I can fill the missing data for numerical values based on the following python code

df.fillna(df.select_dtypes(include='number').mean().iloc[0], inplace=True)

But this will only fill Nan with the overall mean. I have a column with categorical variables and I need to fill the mean values based on the categories in this column.

Answer 1

您可以使用groupby().transform()将组的平均值放置在每一行，然后您可以fillna ：

df.fillna(df.groupby('category_column').transform('mean'), inplace=True)