Documentation for formulae?

I think I am being stupid, but I can’t find documentation anywhere for the syntax and functions available in formula columns.

In particular, I don’t understand how the join condition (third parameter) of the from_dataset() function works. Suppose I have a schema for outlet (shop branch) data that includes a column “merchant_id”, and I want to look up that id into the merchant (parent company) dataset to include the column. The merchant dataset contains columns id and name (amongst others).

Why is the formula for the table join not

from_dataset("merchant", "name", "merchant_id": "id")


I am trying that, but it just gives me no values in the target column.

I also have questions about how to use the weighted and dynamic dataset column types - again, I haven’t been able to find documentation that explains how they work.

Clicking on the green check at the end of the formula edit box brings up the help. That’s about as much as I’ve been able to find anyway.

Re: your problem about no values in the target column.

  1. Try removing the quotes around “merchant_id”: “id”. I set up a test using my own dataset, and with the quotes I just got ‘null’ in my target field. Removing the quotes fixed the problem. Notice in the example in the help I mentioned before, there are no quotes in that field → from_dataset("People", "name", id: person_id)
  2. I’ve found solutions by testing with a Dataset Column field first to make sure I have the fields correct. I’ve found errors from that column type are sometimes clearer.