I have the two datasets below and would like to merge them by group in df2. I am not sure how to merge them such that the dates reset for each group (ie. start from the 1st date and end at the last date for each group).
df1:
| Date |
|---|
| 2021-01-01 |
| 2021-01-02 |
| 2021-01-03 |
df2:
| Group |
|---|
| A |
| B |
| C |
dfdesired:
| Date | Group |
|---|---|
| 2021-01-01 | A |
| 2021-01-02 | A |
| 2021-01-03 | A |
| 2021-01-01 | B |
| 2021-01-02 | B |
| 2021-01-03 | B |
| 2021-01-01 | C |
| 2021-01-02 | C |
| 2021-01-03 | C |
any help would be appreciated
CodePudding user response：
You need to perform cross join. Here is what I would suggest:
# Creating a dummy column to perform a join
df1["Dummy"] = 1
df2["Dummy"] = 1
# to obtain the cross join we will merge on the dummy column and drop it.
df_desired= pd.merge(df1, df2, on ='Dummy').drop("Dummy", 1)