根据最高编号将类分配给ID。 子类 - 熊猫

Question

So actually I have a dataframe with some videoID under which there is a chain of videos with subcategories and I want to assign the highest occurring class. So my dataframe looks like this,

videoId   postId   class

12234     788         1
12234     789         1
12234     790         3
12234     791         4
12234     792         1
12234     793         4

So I want a dataframe like this for every such videoId:

videoId   class
  12234      1

Since highest occurring class is 1 (counting he subposts classes) under that videoId

Now suppose if I have a tie between the classes say like this:

videoId   postId   class

1620      34          1
1620      35          1
1620      36          2
1620      37          2

I want it to be like this:

 videoId  class
 1620      1
 1620      2

So when, there is a tie between the subclasses I want all of them to appear for that videoId . I have tried several w ays, by doing value_counts() , max() , etc. but was not able to reach to the solution.

Answer 1

You can simply apply mode over groupby and reset index ie

df.groupby('videoId')['class'].apply(pd.Series.mode).reset_index(level=0)

  videoId  class
0     1620      1
1     1620      2

Answer 2

One way to do this is to use dense ranking:

df.groupby('videoId')['class'].value_counts()\
  .rank(method='dense',ascending=False)\
  .rename('ranking')\
  .reset_index()\
  .query('ranking == 1')

Output:

   videoId  class  ranking
0     1620      1      1.0
1     1620      2      1.0