filter function returned a Series, but expected a scalar bool (Pandas)

Question

I’m working with a DataFrame which contains columns like [‘Product Name’,’Sales’,’ID’ …] so I’m grouping by Product Name and then computing the Standard Deviation Population for the column ‘Sales’ in order to filter the records using that value.

I tried with this solution

groupedDF.filter(lambda x: x['Sales'].agg(np.std,ddof = 0) != 0 )

But it’s returning this error

TypeError: filter function returned a Series, but expected a scalar bool

Asked By: Jean Paul Sierra Boom

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Source

Answer 1

df = pd.DataFrame({'ID':[1,1,2,2,3,3], 
                   'YEAR' : [2011,2012,2012,2013,2013,2014], 
                   'V': [0,1,1,0,1,0],
                   'C':[0,11,22,33,44,55]})


# This returns a std for every single value
print(df.groupby('ID').apply(lambda x: x['C'].agg(np.std, ddof=0) !=0))

# This returns and std for every group
print(df.groupby('ID').apply(lambda x: np.std(x['C'], ddof=0)!=0))
# This is probably what you want
print(df.groupby('ID').filter(lambda x: np.std(x['C'], ddof=0)!=0))

Answered By: Chris

filter function returned a Series, but expected a scalar bool (Pandas)

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