coalesce() and fill()

Hi Amal! You can think of coalesce() as a much simpler join or case_when(), if you have multiple columns with the same information that you need to merge to simplify your dataset. That is quite common on survey datasets, where you have columns that are actually different answer options and the cells are populated with the same values as the columns, like in the example below:

| first grade    |   second grade  |
| -------------- | --------------- |
|      NA        |  second grade   |
|      NA        |  second grade   |
|  first grade   |       NA        |

Here are some other use cases:

• Cleaning survey data: If respondents could answer the same question in multiple fields (e.g., corrected responses), take the first valid response.
• Combining multiple data sources: If a dataset has the same variable from different systems (e.g., email_primary, email_backup), coalesce() picks the first available value.
• Filling missing data: Replace NA values in a column using values from another column (e.g., use shipping_address if billing_address is missing).

Hi Gracielle Thank you so much for shedding light on this!