I have a dataframe that looks something like this:

I want to replace the descriptions of the items with the most frequent description based on the group # or the first instance if there is a tie.

So in the example above: Chips Ketchup (1 instance) is replaced with Chips BBQ (2 instances) And Cereal Chocolate is replaced with Cereal Honey (First Instance).

Desired output would be:

If this is too complicated I can settle for replacing with simply the first instance without taking frequency into consideration at all.

Thanks in advance

CodePudding user response：

You can use

df['Description'] = df.groupby('Group')['Description'].transform(lambda s: s.value_counts().index[0])

It seems like Series.value_counts (unlike Series.mode, which I also tried) orders elements that occur the same number of times by their first occurence. This behavior is not documented so I'm not sure you can rely on it.