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sample a dataframe based on priority



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern)
Data science time! April 2019 and salary with experience
The Ask Question Wizard is Live!Selecting multiple columns in a pandas dataframeAdding new column to existing DataFrame in Python pandasDelete column from pandas DataFrame by column name“Large data” work flows using pandasHow to iterate over rows in a DataFrame in Pandas?Select rows from a DataFrame based on values in a column in pandasPandas Dataframe split in to sessionsGet list from pandas DataFrame column headersReplace some specific values in pandas column based on conditions in other columnconcate 2 dataframes having keys of first not in another



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0















I have a dataframe like



import random
import pandas as pd
col1 = random.choices([1,2,3,4,5],k=50)
col2 = random.choices(['A','B','C'],k=50)
df = pd.DataFrame('values':col1,'priority':col2)


I want to pull a sample of 25, but if 25 have priority 'A', I want those 25. if 30 have priority 'A', I want 25 chosen from that 30. if 20 have priority 'A', I want those 20, and a random 5 from the 30 with priority 'B'. If 10 have priority 'A' and 10 have priority 'B', I want all 10 'A' and all 10 'B', and 5 random 'C'.



The only way I can think to do this is split the dataset into 3, and then use if statements like



if len(df_A) ==25:
output = df_A
elif len(df_A) >25:
output = df_A.sample(n=25)
elif len(df_A) + len(df_B) == 25:
output = pd.concat([df_A,df_b])


and so on.
Is there a better way to do this? possibly something that scales up to a larger number of priority groups?










share|improve this question






















  • I just had the idea to randomize the dataframe, then use sort and take the top 25 of the dataframe. I think this will work.

    – Phil
    Mar 8 at 21:57






  • 1





    df.sample(frac=1).sort_values(by='priority').head(25)

    – user3483203
    Mar 8 at 21:57

















0















I have a dataframe like



import random
import pandas as pd
col1 = random.choices([1,2,3,4,5],k=50)
col2 = random.choices(['A','B','C'],k=50)
df = pd.DataFrame('values':col1,'priority':col2)


I want to pull a sample of 25, but if 25 have priority 'A', I want those 25. if 30 have priority 'A', I want 25 chosen from that 30. if 20 have priority 'A', I want those 20, and a random 5 from the 30 with priority 'B'. If 10 have priority 'A' and 10 have priority 'B', I want all 10 'A' and all 10 'B', and 5 random 'C'.



The only way I can think to do this is split the dataset into 3, and then use if statements like



if len(df_A) ==25:
output = df_A
elif len(df_A) >25:
output = df_A.sample(n=25)
elif len(df_A) + len(df_B) == 25:
output = pd.concat([df_A,df_b])


and so on.
Is there a better way to do this? possibly something that scales up to a larger number of priority groups?










share|improve this question






















  • I just had the idea to randomize the dataframe, then use sort and take the top 25 of the dataframe. I think this will work.

    – Phil
    Mar 8 at 21:57






  • 1





    df.sample(frac=1).sort_values(by='priority').head(25)

    – user3483203
    Mar 8 at 21:57













0












0








0








I have a dataframe like



import random
import pandas as pd
col1 = random.choices([1,2,3,4,5],k=50)
col2 = random.choices(['A','B','C'],k=50)
df = pd.DataFrame('values':col1,'priority':col2)


I want to pull a sample of 25, but if 25 have priority 'A', I want those 25. if 30 have priority 'A', I want 25 chosen from that 30. if 20 have priority 'A', I want those 20, and a random 5 from the 30 with priority 'B'. If 10 have priority 'A' and 10 have priority 'B', I want all 10 'A' and all 10 'B', and 5 random 'C'.



The only way I can think to do this is split the dataset into 3, and then use if statements like



if len(df_A) ==25:
output = df_A
elif len(df_A) >25:
output = df_A.sample(n=25)
elif len(df_A) + len(df_B) == 25:
output = pd.concat([df_A,df_b])


and so on.
Is there a better way to do this? possibly something that scales up to a larger number of priority groups?










share|improve this question














I have a dataframe like



import random
import pandas as pd
col1 = random.choices([1,2,3,4,5],k=50)
col2 = random.choices(['A','B','C'],k=50)
df = pd.DataFrame('values':col1,'priority':col2)


I want to pull a sample of 25, but if 25 have priority 'A', I want those 25. if 30 have priority 'A', I want 25 chosen from that 30. if 20 have priority 'A', I want those 20, and a random 5 from the 30 with priority 'B'. If 10 have priority 'A' and 10 have priority 'B', I want all 10 'A' and all 10 'B', and 5 random 'C'.



The only way I can think to do this is split the dataset into 3, and then use if statements like



if len(df_A) ==25:
output = df_A
elif len(df_A) >25:
output = df_A.sample(n=25)
elif len(df_A) + len(df_B) == 25:
output = pd.concat([df_A,df_b])


and so on.
Is there a better way to do this? possibly something that scales up to a larger number of priority groups?







python pandas






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Mar 8 at 21:52









PhilPhil

274




274












  • I just had the idea to randomize the dataframe, then use sort and take the top 25 of the dataframe. I think this will work.

    – Phil
    Mar 8 at 21:57






  • 1





    df.sample(frac=1).sort_values(by='priority').head(25)

    – user3483203
    Mar 8 at 21:57

















  • I just had the idea to randomize the dataframe, then use sort and take the top 25 of the dataframe. I think this will work.

    – Phil
    Mar 8 at 21:57






  • 1





    df.sample(frac=1).sort_values(by='priority').head(25)

    – user3483203
    Mar 8 at 21:57
















I just had the idea to randomize the dataframe, then use sort and take the top 25 of the dataframe. I think this will work.

– Phil
Mar 8 at 21:57





I just had the idea to randomize the dataframe, then use sort and take the top 25 of the dataframe. I think this will work.

– Phil
Mar 8 at 21:57




1




1





df.sample(frac=1).sort_values(by='priority').head(25)

– user3483203
Mar 8 at 21:57





df.sample(frac=1).sort_values(by='priority').head(25)

– user3483203
Mar 8 at 21:57












0






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