Adding a new column to a dataframe

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Adding a new column to a dataframe - lokhtar - Jan-14-2021

Hello,

I am working with covid-19 data, and I am trying to add a new column to the dataframe based on the datetime, converting it to a day of the week.

import pandas as pd

url='https://raw.githubusercontent.com/nytimes/covid-19-data/master/us-states.csv'
data = pd.read_csv(url)
data.head()

The output of that looks like this:

Output:date	state	fips	cases	deaths
0	2020-01-21	Washington	53	1	0
1	2020-01-22	Washington	53	1	0
2	2020-01-23	Washington	53	1	0
3	2020-01-24	Illinois	17	1	0
4	2020-01-24	Washington	53	1	0

What I want to do, is to add a column called 'dow' that converts the date into the actual day of week.

So I tried this:

data['DOW'] = datetime.date(data['date']).strftime('%A')

But that is giving me this error:

Error:TypeError                                 Traceback (most recent call last)
<ipython-input-33-ae85c40abf8d> in <module>()
      1 data['DOW'] = 'Day'
----> 2 print(datetime.date(data['date']).strftime('%A'))

/usr/local/lib/python3.6/dist-packages/pandas/core/series.py in wrapper(self)
    127         if len(self) == 1:
    128             return converter(self.iloc[0])
--> 129         raise TypeError(f"cannot convert the series to {converter}")
    130 
    131     wrapper.__name__ = f"__{converter.__name__}__"

TypeError: cannot convert the series to <class 'int'>

I would appreciate any help!

RE: Adding a new column to a dataframe - buran - Jan-14-2021

import pandas as pd
 
url='https://raw.githubusercontent.com/nytimes/covid-19-data/master/us-states.csv'
data = pd.read_csv(url, parse_dates=['date'])
data['DOW'] = data['date'].apply(lambda x: x.strftime('%A'))

# if you don't want to convert date columne:
# data = pd.read_csv(url)
# data['DOW'] = pd.to_datetime(data['date']).apply(lambda x: x.strftime('%A'))

print(data.head())

Output:         date       state  fips  cases  deaths        DOW
0  2020-01-21  Washington    53      1       0    Tuesday
1  2020-01-22  Washington    53      1       0  Wednesday
2  2020-01-23  Washington    53      1       0   Thursday
3  2020-01-24    Illinois    17      1       0     Friday
4  2020-01-24  Washington    53      1       0     Friday

In the example I convert date column to datetime object when I read the csv file. In the comments - example if you do not want to convert it

RE: Adding a new column to a dataframe - buran - Jan-14-2021

Also

data['DOW'] = data['date'].dt.strftime('%A')

data['DOW'] = data['date'].dt.day_name()

where date columns is already converted to datetime