how to select the data of a Dataframe (Python)

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how to select the data of a Dataframe (Python)

ktflash

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Points: 1400

March 4, 2022 at 12:55 pm

#3993042

ahoi,

i have gotta admit i struggle a bit with the querying of data from hierarchical indexed dataframes.

Heres the dataframe creation.

import pandas as pd
import numpy as np

multi_indexed_DF = pd.DataFrame(np.random.rand(4, 2),
index=[['a', 'a', 'b', 'b'], [1, 2, 1, 2]],
columns=['data1', 'data2'],)

How do i comebine the first 2 selection methods (filter_1, filter_2) to get a propery combination of both filters:

# get only columns data1,data2 from first index with 'a', 'b' and for each one only the 2nd index val=1
filter_1 = multi_indexed_DF.loc[(['a','b'], 1), ['data1','data2']]

# get only those entries where data1 is more than 0.5 (random numbers so the result varies)
filter_2 = multi_indexed_DF.loc[multi_indexed_DF.data1 > 0.5]

# so my question is how do i add the 2nd filter of data1 > 0.5 on on top of the first selection
# the full dataframe multi_indexed_DF, filter_1, filter_2
# this one seems to work, but the system tells me not to use it because its depricated and will be gone 
# so i am looking for the "proper" way(s) toactually write this 
filter_3 = multi_indexed_DF[multi_indexed_DF.data1 > 0.5].loc[(['a','b'], 1), ['data1','data2']]

"""
# here is the result example from an execution with random numbers of mine for
# FULL
        data1     data2
a 1  0.295029  0.815447
  2  0.481834  0.529683
b 1  0.981762  0.021112
  2  0.995068  0.579253 

# Filter 1
        data1     data2
a 1  0.295029  0.815447
b 1  0.981762  0.021112 

# Filter 2
        data1     data2
b 1  0.981762  0.021112
  2  0.995068  0.579253

# Execpted Result for combined Filter 3: result of filter 1 without index a 1 because a data1 > 0.5
        data1     data2
b 1  0.981762  0.021112 
"""

Thanks

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April 25, 2022 at 2:03 pm

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Site Owners SSC Guru Points: 80330 More actions · Answer 1

Thanks for posting your issue and hopefully someone will answer soon.

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