I think you might be running into an issue we're tracking which causes custom fields to lose their type info, meaning that they're not correctly being treated as numeric fields, so Metabase is filtering them out when you try to choose them as the target of your aggregation:
Hi @kimcha were you ever able to resolve this issue? Im using V.32.4 - built a question that counts then pivots the values to create two columns and would then like to create a custom field that expresses a ratio of the two values. I tried creating a second question that used the first as its data source but the custom filed option doent seem to be available when the data source is a “saved question”. Any pointers appreciated.
I would recommend that you upgrade to 0.32.8 - several issues with earlier 0.32.x
I’m not quite sure I understand where your problem is - Pivot or Custom Field or Saved Question?
Can you explain a bit more - or provide a screenshot if that makes it easier?
Dear @flamber I create a question that pivots the data correctly:
I want to add a custom field to the pivot that calculates the ratio of the two numeric columns:
| State | 2017 | 2018 | ratio |
| MN | 1 | 4 | 0.25 |
| MA | 2 | 2 | 1 |
| NY | 10 | 100 | 0.1 |
but the pivot columns 2017 & 2018 are not listed as possible fileds in the Custom Field option, hence why I tried to use the pivot question as the data source for a new question, hoping that the columns would then be available to create a custom expression.