如何根据日期合并两个不同大小的数据框

Question

I am trying to merge two dataframes based on a date column with this code:

data_df = (pd.merge(data, one_min_df, on='date', how='outer'))

The first dataframe has 3784 columns and the second dataframe has 3764. Every date in the second dataframe is also within the first dataframe. I would like to get the dataframes to merge on the date column with any dates that the longer dataframe has being left as blank or NaN etc.

The code I have here gives the 3764 values followed by 20 empty rows, rather than correctly matching them.

Answer 1

Try this:

data['date'] = pd.to_datetime(data['date'])
one_min_df['date'] = pd.to_datetime(one_min_df['date'])
data_df = pd.merge(data, one_min_df, on='date', how='left')