If your data is quantitative then go for mean or median. Mean meadian returns and works as same ways both returns a series. Group by 2 colums and fillna with mode.
Medians and categorical data Even though the median may be carefully defined as the middle value in an ordered data set students sometimes try to find the median of categorical data sets.
In this case analysts tend to use the mean because it includes all of the data in the calculations. But mode returns a dataframe. Draw a vertical line on the chart where you estimate the mode the mean and the median values to be. Mode is not compatible with fillna as same as mean median.