CODEWITHSUNDEEP
pythonpandasdataframenumpydatetime
Andres Perez
Andres Perez

Reputation: 23

Using np.select in DateTime series - Pandas Python

I have a problem using np.select in DateTime series. Imagine you have a DataFrame: dateframe['id','FLOAT','DATE1','DATE2']

dateframe['DATE1'] = dt.datetime.now()
dateframe['DATE2'] = dt.datetime.now()

dateframe['DATE3'] = np.select(
    [
        dateframe['FLOAT']>0,
        dateframe['FLOAT']<=0,
    ],
    [
        dateframe['DATE1'],
        dateframe['DATE2'],
    ]
)

I get this error:

TypeError: The DTypes <class 'numpy.dtype[uint8]'> and <class 'numpy.dtype[datetime64]'> do not have a common DType. For example they cannot be stored in a single array unless the dtype is object.

Thanks in advance.

Upvotes: 2

Views: 791

Answers (1)

David Erickson
David Erickson

Reputation: 16683

use np.where when you have one condition that creates exactly two mutually exclusive groups:

dataframe['DATE1'] = dt.datetime.now()
dataframe['DATE2'] = dt.datetime.now()
dataframe['DATE3'] = np.where(dataframe['FLOAT']>0,dataframe['DATE1'],dataframe['DATE2'])
dataframe

Regarding the error with np.select. Initially store the date as an object datatype with str() and then convert to_datetime() later. Per the error, there is an issue with the datetime data type in the np.select statement

dataframe['DATE1'] = str(dt.datetime.now())
dataframe['DATE2'] = str(dt.datetime.now())
dataframe['DATE3'] = pd.to_datetime(np.select([(dataframe['FLOAT']>0),(dataframe['FLOAT']<=0)],
                                              [dataframe['DATE1'],dataframe['DATE2']]))
dataframe

Upvotes: 2

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