I have a weather dataset, it gave me many years of data, as below:

I am trying to get the daily rainfall, starting from the end of the month subtracting the previous day. For eg:

Thanks for your efforts in advance.

CodePudding user response：

Try:

# Convert to datetime if it's not already the case
df['Date'] = pd.to_datetime(df['Date'])

df['rainfallDaily'] = df.groupby(df['Date'].dt.month)['rainfallInMon'].diff().fillna(0)
print(df)

# Output
        Date  rainfallInMon  rainfallDaily
0 2009-01-01           0.00           0.00
1 2009-01-02           0.03           0.03
2 2009-01-03           0.05           0.02
3 2009-01-04           0.05           0.00
4 2009-01-05           0.06           0.01
5 2009-01-29           0.20           0.14
6 2009-01-30           0.21           0.01
7 2009-01-31           0.21           0.00
8 2009-02-01           0.00           0.00
9 2009-02-02           0.00           0.00

CodePudding user response：

I have a weather dataset, it gave me many years of data:

df['rainfallDaily'] = df.groupby(df['Date'].dt.to_period('m'))['rainfallInMon'].diff().fillna(0)

Or:

df['rainfallDaily'] = df.groupby(pd.Grouper(freq='M',key='Date'))['rainfallInMon'].diff().fillna(0)