Hi @texodus, could you take a look this PR to let me know if anything is amiss, thanks.

Thanks for submitting this! Although this succeeds for simple cases, it does not work for more complex examples. Luckily the code you wrote is on the right path, it only needs to be generalized further.

Here is a config that shows that your fix is not enough. Using the example data from #2575 and the file example, providing more than 1 split overwhelms your fix. Instead of hardcoding one level of split, you need to allow for any number of splits.

{
  "version": "3.1.0",
  "plugin": "X/Y Line",
  "plugin_config": {},
  "columns_config": {},
  "settings": true,
  "theme": "Pro Light",
  "title": null,
  "group_by": [
    "exam_month"
  ],
  "split_by": [
    "exam_subject",
    "teacher"
  ],
  "columns": [
    "exam_month",
    "exam_score",
    null
  ],
  "filter": [],
  "sort": [],
  "expressions": {},
  "aggregates": {
    "exam_score": "avg",
    "exam_month": "any"
  }
}

To apply the config you can use the debug panel provided in the top right of the sidebar.

Also, We generally require a unit test for any fix, regardless of complexity. If you could write a unit test that ensures that this functionality works, it would be amazing!

Again thanks for your work in fixing this issue, I hope we can get this merged soon!

@sinistersnare Thanks for the feedback and suggestions. I'll work on it further.