CODEWITHSUNDEEP
pythonpandastime-series
Thanh Nguyen
Thanh Nguyen

Reputation: 912

Pandas Set all value in a day equal to data of a time of that day

Generating the data

random.seed(42)
date_rng = pd.date_range(start='1/1/2018', end='1/08/2018', freq='H')
df = pd.DataFrame(np.random.randint(0,10,size=(len(date_rng), 3)),
                  columns=['data1', 'data2', 'data3'],
                  index= date_rng)
daily_mean_df = pd.DataFrame(np.zeros([len(date_rng), 3]),
                             columns=['data1', 'data2', 'data3'],
                             index= date_rng)
mask = np.random.choice([1, 0], df.shape, p=[.35, .65]).astype(bool)
df[mask] = np.nan

df
>>>
                 data1 data2 data3
2018-01-01 00:00:00 1.0 3.0 NaN
2018-01-01 01:00:00 8.0 5.0 8.0
2018-01-01 02:00:00 5.0 NaN 6.0
2018-01-01 03:00:00 4.0 7.0 4.0
2018-01-01 04:00:00 NaN 8.0 NaN
... ... ... ...
2018-01-07 20:00:00 8.0 7.0 NaN
2018-01-07 21:00:00 5.0 4.0 5.0
2018-01-07 22:00:00 NaN 6.0 NaN
2018-01-07 23:00:00 2.0 4.0 3.0
2018-01-08 00:00:00 NaN NaN NaN

I want to select a specific time each day, then set all value in a day equal to the data of that time. For example, I want to select 1:00:00, then all data of 2018-01-01 will be equal to 2018-01-01 01:00:00, all data of 2018-01-02 will be equal to 2018-01-02 01:00:00,etc.,

I know how to select the data of the time:

timestamp = "01:00:00"
df[df.index.strftime("%H:%M:%S") == timestamp]

but I don't know how to set data of the day equal to it.

Thank you for reading.

Upvotes: 1

Views: 142

Answers (1)

BENY
BENY

Reputation: 323226

Check with reindex 

s=df[df.index.strftime("%H:%M:%S") == timestamp]
s.index=s.index.date
df[:]=s.reindex(df.index.date).values

Upvotes: 2

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