How to find percentage of a value in a column by grouping by other multiple columns?

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I want to find the percentage of rows in a column that has a certain value. And find the percentage for each combination of two other columns.

Here is a example df:

data =[['North Shields','UK','Y'],['North Shields','Foreign','N']]
df = pd.DataFrame(data, columns = ['Port','Type','Shellfish Licence licence (Y/N)']
df

i have tried the following but get a key error, probably because i cant grouby two columns in this way.

port_shel_df = landing_fish_merge['Shellfish Licence licence 
(Y/N)'].eq('Y').groupby(port_merge_lic_df['Port','Type]).mean().reset_index(name='Shellfish 
license 
percentage')
port_shel_df = port_shel_df.set_index('Port')
port_shel_df[:1]
pandas dataframe python
1 Answers

Create helper column and aggregate by it:

df = (landing_fish_merge.assign(new= landing_fish_merge['Shellfish Licence licence (Y/N)'].eq('Y'))
                        .groupby(['Port','Type'])['new'].mean()
                        .reset_index(name='Shellfish license percentage'))
user_29010020
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