CODEWITHSUNDEEP
pythonpandasdataframemulti-index
s900n
s900n

Reputation: 3375

Randomly sample levels in a MultiIndexed DataFrame

Hi I have a multi index dataframe like below and I want to randomly select part of this dataframe according to ID_1:

Below is my Dataframe 

ID_1 ID_2 feature_1 feature_2 
  1    1      0        0
       2      1        1 
  2    1      1        1 
       2      0        1    
  3    1      1        1 
       2      0        1  
  4    1      1        1 
       2      0        1

and I want to select 2 of ID_1's out of 4. Example result: 

ID_1 ID_2 feature_1 feature_2 
  2    1      1        1 
       2      0        1    
  4    1      1        1 
       2      0        1

What is the best way to do this. Thank you.

Upvotes: 1

Views: 377

Answers (1)

cs95
cs95

Reputation: 402613

Use np.random.choice and select 2 levels at random from df.index.levels[0]. You can then use the selected levels to index into df using df.loc.

df
           feature_1  feature_2
ID_1 ID_2                      
1    1             0          0
     2             1          1
2    1             1          1
     2             0          1
3    1             1          1
     2             0          1
4    1             1          1
     2             0          1

# np.random.seed(0)  # Uncomment to make results reproducible.
df.loc[np.random.choice(df.index.levels[0], 2, replace=False)]

           feature_1  feature_2
ID_1 ID_2                      
3    1             1          1
     2             0          1
4    1             1          1
     2             0          1

If you need to do the same thing for the first level, use pd.IndexSlice for slicing on the first level.

v = np.random.choice(df.index.levels[1], 2, replace=False)
df.loc[pd.IndexSlice[:, v], :]
# df.loc(axis=0)[pd.IndexSlice[:, v]]

Upvotes: 1

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