DataFrame.resample does not include last row

Question

So i wanted to downsampling my data using ffill method

I have a data:

2020-01-01  1.248310e+06
2021-01-01  1.259511e+06
2022-01-01  1.276312e+06
2023-01-01  1.298714e+06

The output should be:

2020-01-01  1.248310e+06
2020-02-01  1.248310e+06
2020-03-01  1.248310e+06
....        ...
2023-10-01  1.298714e+06
2023-11-01  1.298714e+06
2023-12-01  1.298714e+06

Here is what I tried

 down_sampling = df.resample('MS', fill_method= 'ffill')

I get something like:

2020-01-01  1.248310e+06
2020-02-01  1.248310e+06
2020-03-01  1.248310e+06
....        ...
2022-11-01  1.276312e+06
2022-12-01  1.276312e+06
2023-01-01  1.298714e+06

The problem here is the year 2023 has only one month.

Can you suggest any idea on how to fixed it.

Thank you.

Asked By: Somphon Rueangari

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Source

Answer 1

You can do it like this:

index = pd.date_range('1/1/2020', periods=4, freq='YS')
series = pd.Series([1.248310e+06, 1.259511e+06, 1.276312e+06, 1.298714e+06], index=index)
series2 = pd.Series(1.298714e+06, pd.date_range('12/1/2023', periods=1))
series = series.append(series2)
down_sampling = series.resample('MS').ffill()

Answered By: Akaisteph7

Answer 2

A hacky but pythonic solution:

df.append(df.iloc[[-1]].set_index(df.iloc[[-1]].index.shift(1, freq="D"))).resample("H").ffill()[:-1]

It picks the last row (as a df: df.iloc[[-1]]),

increases its index by one step (here 1 day: .index.shift(1, freq="D")),

then resamples: .resample("H").ffill()

And removes the single dummy row at the end of df ([:-1])

I’d actually expect closed: parameter of resample to do the job.

Answered By: Amir P

DataFrame.resample does not include last row

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